I've had trouble saying no in the past, but there are a few things you can do to not put yourself in this position again.
- don't go to his place at the end of the night
- once you say no, if he doesn't respect it stop arguing and leave
- watch your alcohol intake because it removes inhibitions
If you like a guy and decide you wouldn't mind sleeping with him, take control of the situation. You decide the time and place and the essential protection.