There have been cheaters as long have there have been relationships. From Clinton to Schwarzenegger to Madonna, the reasons are the same; they say they are looking for more appreciation, feel unwanted or undervalued, or they are just plain self-centered. But if your partner is cheating, how can you tell?

1. They stay out late, because they're "busy at work," or "their friend really needs them." This could be true, but is it happening more frequently than it used to? Is the behavior progressing to him missing dinners or her not showing up for lunches anymore?

2. They are suddenly more or less complementary than they used to be. Is he telling you that you look absolutely stunning in that dress you've had for years; the same dress he had told you before he hated? Is she saying you look like you've been working out when you know for a fact that you've gained 15 pounds, and these pants don't really fit?

3. He or she is spending a lot of time on his or her phone or is privately texting or talking when you aren't around. They take their phone with them everywhere and never leave it laying around, and they seem unwilling to give you their password to unlock anything.

4. They are unreachable at times - their phone might be turned off, or when you call them at the office, they aren't in when they are supposed to be. They might have business trips unexpectedly, and the hotel numbers never seem to get through.

5. You hear stories that don't match up; they break dates without explanation or contradict themselves when they are talking about things that happened at "that thing last weekend."

6. They smell different. This might sound odd, but a man will change his cologne for a partner, or a woman will receive a gift of new perfume. If they act guilty and can't clearly answer where it came from - that's definitely a red flag.

7. You're getting fewer public displays of affection. If he or she is affectionate only in private and almost goes overboard at times, this may or may not be a show of guilt. It may also mean that your partner is reserved in public.

8. Have you found any jewelry in the car that isn't yours? Or a cufflink in the glove compartment when you were looking for your registration? There could be another explanation, or not. Maybe it's time you asked.

9. If there are suddenly unexplained expenses on your account or unexpected withdrawals, this may be cause for some alarm. Hotels, gifts and eating out leave a trail of behavior. Sometimes these unexplained expenses are innocent, but may not be.

10. Another thing to watch out for is your partner accusing you of being paranoid. That may seem true if they aren't cheating on you, but if they are hiding something, your partner may use that accusation to manipulate you. It's time to talk about your partner's behavior, and why you are feeling this way.

What it really comes down to is honesty. Be sincere and tell your partner that telling you the truth will help the both of you. If your feelings are being hurt by something they are doing, be open about it. It could be a misunderstanding that some honest communication will clear up, but it could be that they are seeing someone else. Talking about it will help you move on to someone with more respect and integrity whom you deserve.