Wht da hel is wrong with me???

i got out of a 5yr old relationship last year.. its been almost a year now and i hav began liking guys and getting bak to datin.. but the problem is tht i like a guy (generally) in the beginning and feel excited abt it.. but once i know he is into me too and we start dating i start holding bak and decide to ditch him.. i hav done this to 3 diff guys.. all of them were great in terms of everything.. and i am no longer in love with my ex of 5 yrs.. but then y am i not able to be stable or even sty with any of these guys for long enuf.. all the guys are great in their own ways but i dont know wats wrong with me.. i am with this guy now.. who i used to like a lot before and now i some how hav lost interest in him.. and he is a really nice guy and likes me a lot too.. i feel weird.. help me!!!!