Im scared of making the wrong decision, major help please!!?

i've been with my boyfriend since i was 15, so yes i was his first and he was mine and i couldnt imagine doing it with nobody else. then last year times got tough! he finished me, i found out he kissed a girl he denied it but i caught him out then i found out that he slept with this girl, i spoke to the girl and she admitted it they done it three times and he missed my nieces christening to go over her house and we were all out one night and he dissappeared and turned his phone off and i was on my own in tears and i found out he slept over this girls house i was devasted but of course hes denying it and admitted to doing it once at a uni party and he was paraletic drunk! then the other day my best friend told me that he slept with this other girl and apparently he kept asking her to go over his and then one night after clubbing she apparently slept over his, but his parents are strict and wouldnt even allow me in there house, is he being honest saying nothing happened, i dont know what to believe. he has a thing for lying :'( so its really hard, should i end it? but i want to be with him just cant cope with anymore lies and knowing hes been around and hes still my first and i havent even kissed anyone on our breakups. help please? need some serious advice :'(