Boyfriend drinks occassionaly; blacks out; talks to women; doesnt remember

Been w/ BF for 1 year. He drinks occassionally, but blacks out due to his psych meds that he takes. I truly believe he blacks out. I have seen/witnessed this myself. A couple of times we have woken up to the computer screen showing him chatting with women; getting their number; and even calling them. The 1st time this was revealed I was pissed--but he sucked me back in--blaming the blackout. He said he would quit the heavy drinking. 2nd time(within a week)--same excuse--same apology. 3rd time(within a week)--same excuse--apology--but this time he has not gone back to the drinking. It has been 3 months. He asked me to help him, his parents, because he does not want to jeopardize our relationship etc. I will help him of course. But, I am an idiot for staying? My friends say "Alcohol is not an excuse". Just because I say "i have seen him blackout" is that just my excuse? denial to myself?