1. He has a lot of girlfriends that he speaks to regularly, which you have never met.
2. When the relationship seems natural in progression to next steps, he get really spooked.
3. He has cheated on past girlfriends.
4. One of his parents, or both cheated on one another.
5. He accuses you of cheating and is very insecure.
6. Your friends dislike him or seem apprehensive.
7. His friends are all cheaters.
8. He is secretive, and commonly gets caught up in lies he has made up.
9. He uses alcohol and/or drugs. This is an even stronger red flag if he uses them while you are not with him.
10. He tries to belittle you, even subtly, so that you will be more concerned with this then what he is up to.
11. Anytime you bring up the fact that you have a trust issue, he dodges the question by making you seem crazy.
12. Selfishness in excess.
13. When sex becomes dull, or non existent.
14. When intimacy seems scary and makes them uncomfortable. Big sign of guilt.
15. When they won't let you near their computer, phone, etc...
Relationships are immensely hard, relationships with a cheater are impossible. No, I do not believe cheaters ever change nor do I believe someone can change them. They have a serious problem with always wanting more, or what they can't have and even if you're married with 2 kids, it will still be an issue. Find a REAL man with a secure being that can treat you the way you need and deserve to be treated... and for lack of a better word, fuck them. If your man candy acquires more then half of the list above... get out while you can... you can thank me later.