Be in a healthy relationship

Since i started dating it seems like everything is perfect in the beginning and then i start flirting with other guys while i am in a serious relationship … i wanna stop cheating on my partners and actually find someone im serious about and settle down… but its so hard because i feel like my partner is probably out there fucking me over so i dont want to be heartbroken and stalkerish and begging for some1 2 be with me so i think that when u have someone on the side ur attention is not focused on 1 person .. i guess im afraid 2 give my all cuz then i might be to dependant on them and im a very sensitive person so if some1 says anything to me that i dont wanna hear it hurts .. and i was in a 5 year relationship which i was so in love with him until i would find out that he was goin 2 clubs and talking to girls behind my back and he use to be like veryyyyy in love wid me 2 the point where he was obsess so why would he do stuff like dat ? then when we broke up he stop changed so much … he became a major asshole so its been 2 years that we broke up .. i cheated on him multiple times that he knows about and he still took me back but then the reason why we broke up is because i lefted him for someone else .. maybe thats why he has resentment towards me … my second relationship was the 1 i was wid for 2 years after my ex … you could say karma came back to me … i was soooooo madly in love with this guy but he never showed me no type of attention he was always goin out and never respecting me but for some reason i held on like an idiot i kept gettin hurt over and over and over again until i finally decide to let go and cheat on him so i started to cheat on him and guys would call my phone while i was wid him or some shit and he started to get really abusive he would beat me up or cuss at me and bring me down like i was the lowest person alive … it got so bad i started to catch anxiety attacks … so yea unfortunaltely im still wid him but i really wanna leave but now wid the anxiety he became a security blanket 2 me .. i dunno what 2 do???? i juss want to leave the relationship widout feeling dependant on him