My rules:
Sex + close friendship= Relationship
Sex + (stranger, acquaintance) = fun night
Friendship - sex= friend
sex + friend's SO= No

I know I can run when things get intense/confusing BECAUSE I don't want to hurt the person with my f'ed-up-ness. I also have sex when I'm on my way down and then seclude myself when it gets to bad. I think you may want to text him and say you'll wait but you need to know for how long.