I'm sorry about your current situation, and like Tim above have no ready answers, just things to think on.
First, yes you might be in your current relationship with someone you do not seem to get on with becuse you moved away and probably looked for the type of relationship that was broken -and looked to hard.
Secondly being unfaithful does not normally just happen for no reason at all, it could be there was something missing from your relationship with your first BF and you looked for it elswhere, anything from it being too serious, your not realizing what you ad, insecurity, an argument or anything else including sex.
Can I suggest you do think about what caused it? You may find a surprising reason. If you do decide waht it was that might change your attitude to the first relationship -or not, you would know best.
I can make suggestions, no idea if they sit well.
First if you are unhappy with your new partner then let him go, there is no point in punishing yourself by hanging on to something that causes greif
Second try to rebuild those friendships that were broken
Third sure, send you ex a letter or whatever, say why you cheated, and ask if he would like to get together to see if the problem can be overcome. Please be careful not to seem to be justifying your actions, just want to be back.
I hope I'm not budding up your hopes, he may well, like you , have formed another realtionship or simply not be interested, Still nothing tried nothing gained.
What do you think?