Should I stay with him?

my boyfriend and i have been togehter since feb. 2010. he admitted tonight after i basically forced him to stop evading the question if he had cheated on me. he finally said yes, a bj. i then asked if there was anything more. he said yes, he had sex (both of these about a year ago). i took the news calmy said good night and drove home, crying and screaming alone. i called him a little later saying i need to get my feelings out now before i resent him. i felt like i got all the anger and saddness out, and then asked him how good he feels to let go of that secret he'd been keeping a year. he said good..but i heard the hesitation in his voice and asked him if there were anymore times. he kissed his ex a few months ago and then drunkely kissed someone else a month ago. he sounds so bad out loud..but he helped through oxycontin addiction and the death of my mother. i told him things ive told no one, and vice versa. please give pros and cons. please i need help.