"If your partner gets easily triggered or offended when you express yourself, they might be trying to hide something that's going on inside of them," Nancy Ruth Deen, a Vancouver-based breakup coach, tells Bustle. If this is out of character for them, something might be up. "Sometimes this is intentional. Other times it's a subconscious defense to avoid actually saying how they're feeling."

But how should you bring it up to them? “Come from a place of love,” says Yue Xu, Co-Host and Co-Creator of the Date/able podcast. “Any time you go into the conversation with a confrontational mindset or pointing fingers at your partner, it's going to make them seem even more guilty than they really are.”

While it's perfectly acceptable to have privacy within a relationship, it's not a great sign if your partner suddenly locks down their devices with elaborate passwords.

"If your partner has passwords that they don't share on all their devices and are constantly using them beyond what makes sense professionally, they are probably discreetly tending to something personal," relationship expert Margaux Cassuto tells Bustle.

A person who's hiding something might not readily admit what's going on, but point out this change and see how your partner responds, Cassuto says. Again, if they get defensive, you may be onto something.

But with that being said, remember that “deliberately withholding information… is a sign of fear,” says Dr. Nan Wise, a cognitive neuroscientist, licensed sex therapist, and author of Why Good Sex Matters. And while it’s important to get answers, it’s also important to give your partner room to respond — especially if they’re afraid.

You may notice that your partner is suddenly less present or seems emotionally distant. And while this can happen for a variety of reasons, it could also be a sign they aren't being entirely truthful. "Partners often will distance themselves as a means for relationship preservation to 'not burden' the partner with whatever they might be hiding," Dr. David Songco, a licensed psychologist at New Insights, LLC, tells Bustle. "This in many ways is paradoxical: Not burdening the partner creates distance, which in turn places burden on the relationship."

Relationship and sexuality educator Dr. Logan Levkoff has also seen this happen. “If you ask a question and your partner gives a deliberately ambiguous answer,” she advises to ask specific follow-up questions, such as “Is there something you don't want to say or something you don't want to tell me? Is there a reason you're not being forthcoming?”

"We often change our habits or daily schedule if we are engaged in new activities, or are trying to make a life change," Elisa Robyn, PhD, a relationship expert who specializes in life transitions, tells Bustle. For example, someone who is thinking about having an affair may change their exercise habits, Robyn says. But just because someone picks up a positive habit doesn't mean they're cheating, lying, or hiding something. To find out more, bring up your concerns to your partner. If the relationship is strong and things are OK, they should be willing to talk about them.

Your partner is wining and dining you, or showering you with gifts. This may not seem like a bad thing, but may be worth looking into if it’s entirely out of character. But before misreading their bouquet, Wise recommends “calming yourself down a little bit and then approaching [the conversation by noting] the actual behaviors that you're observing.”

People tend to project their guilt onto others, so a lying or cheating partner "might accuse you of trying to sneak on their phone or accuse you of not trusting them," psychotherapist Devon Jorge, MSW, RSW, tells Bustle. "This is a manipulation of guilt to get you to show them how much you can and should trust them."

The same can be true for other secrets. Are they suddenly mad at you for spending too much money, or do they claim you're lying? If so, it could be an act of projection.

Mark Twain has a helpful quote for this relationship situation, “If you tell the truth, you don't have to remember anything.” If someone is hiding something — and thus lying to cover it up — they might have a hard time keeping their stories straight, and inconsistencies could eventually show up. "For example, they mention going out to lunch, but then say they ate at their desk," Robyn says. While not everyone can remember their day in perfect detail, if it keeps happening, it's understandable to feel suspicious. And if the relationship is going to last, you have a right to ask.

On a similar note, you might notice that your partner is suddenly vague in areas where they used to be transparent, Dr. Debra A. Nixon, LMFT, an online counselor with ChatOwl, tells Bustle.

If you ask about their day, they might say it was "fine" instead of going into detail about how they felt or what they did. If you ask how their night was with friends, they might say it was "fun" instead of recounting a few stories. And if you want to talk about the future, they might avoid the topic, even though they used to enjoy making plans.

Speaking of changes, a partner who is hiding something may have a tough time explaining why their day suddenly looks different. For instance, they might have to stay late at work, but give you conflicting reasons, Robyn says. And if you call to check in, there's a good chance they won't pick up the phone.

If they can't give you reasons and details, "they are hiding something about their schedule, which suggests they are doing something they do not want to share," Robyn says.

If a person is hiding something, they’re likely to create a sense of separation, Jorge says, which is why your partner may no longer invite you to be a part of their social, familial, or professional lives. Maybe you used to spend time with their friends, but now they're claiming the hangout will be too "boring.” If the reasons for exclusion don't make sense, that's your cue to get more information. While everyone's entitled to some personal space and alone time, major changes could be a red flag.

Sometimes it isn't so much about what your partner says, but how they act. If they won't look into your eyes, for instance, Robyn says it can be a sign they're lying, as they may be too nervous or stressed to interact. A partner who is hiding something may also be less interested in sex, or close themselves off to affection. Overall, they'll probably seem cold and detached.