Whats has been going on or what is going on anymore?

i dont understand this and need as much help on what to think or what to do in this kind of situation so plz...here we go..........me and this guy have been back and fourth since 8th grade..dating wise and wise of course..in high school it didnt seem like much but calls for the both of us.....yes we did date in school but we never talked and it seemed as tho we just went our own ways not breaking up with each other...hed call for like 2 days strait wed get toghether and do it u know.then he say he call me and never did...but he eventually comes back everytime.we have been toghether for 3 weeks almost now and it has been 3 yrs since we dated..ui dont understand why he comes and goes the way he does?why does he do that?he is keeping up to date with our relationship this time but i dont understand why hes back and fourth and in between.this last guy i dated he tried to stop me from it cuz he liked me and wanted to be with me.but i knew it wouldnt work out.so i moved on..but what should i do...help?!srry so long an d confusing.