How do you gain your boyfriend's trust back after getting high with your ex and trying to keep it from your boyfriend?

is he more hurt that you got high with your ex or that you where with him either way getting high is your first problem i dont know what drugs you use but you cant make good decisions while high even though they may seem great at the time and you wonder why nobody ever thought of that before.. when you sober up youll see they where not good ideas.i know.