How to move on from a cheater?

I met the perfect guy in a summer program, or so I thought. Everyone knew we liked each other, and I thought things couldn’t be more perfect, but then a mutual friend told me that this guy actually had a girlfriend back home. My first instinct was to confront him and then cut the guy out of my life, but he apologized for leading me on and eventually I relented. Now we are just friends and even though he lives more than 2000 miles away, he calls me every week or so. I know he is a cheater and I would NEVER take him if the opportunity arose (he and his girlfriend have fallen out), but I have found it sooo hard to forget that perfect feeling I had before I found out the truth. I will think that I’m ok, and that I will be back to my normal self, but then he will call and I’m not Ok anymore. I’ve actually turned away interested guys because I can’t forget him.

Do you have any advice or tips on how to forget him and move on? In the past, the only way I get over guys is when I get involved with someone else, but I think this is a dangerous pattern.

Also, does anyone have tips on how to spot men who are already in relationships, so a girl doesn’t have to waste her time and emotions on cheaters? Any advice would be greatly appreciated!