After an HIV scare, a college playboy promises God he’d become abstinent, however this proves near impossible as he repeatedly falls into temptation, and begins to doubt he could ever truly change.

I agree with patrockable that there is no clear goal, except that the inciting incident sounds good. I think the characters want needs to be defined. It could simply be a closer walk with God or a girl. If you can come up with an original sounding goal, it would be a strong log line.

Also, it leaves it somewhat unclear that this man is heterosexual. I assume he is because you did not mention any thoughts on homosexuality.

Good points all good points, I have some work to do, thanks.

Your character needs a clear obtainable goal. Staying abstinent indefinitely doesn't promise a conclusion.

Also, the stakes still aren't that high. What will happen if he sleeps with someone? He'll feel guilty, go to confession....and that's it.

What if he falls in love with a girl, but she knows about his reputation, so she says, if you can stay abstinent for 3 months, then I'll be with you?

Or he has a life changing calling to be a priest, and the bishop says, if you can stay abstinent for 3 months, then I'll consider you?