Most Helpful Guy
Personally I would appreciate it if a girl told me about it before we get to sex. I would probably say "no" and just wait for a better time. I'm cool with waiting a bit. I am of course speaking for myself and not for other guys.
Most Helpful Girl
If you feel like it's getting intimate again, simply explain that it's the wrong time of the month and that you can't have sex. Even though many men don't want to hear about periods, they fully understand so don't feel embarrassed by it. My first time with my boyfriend, I had my periods, we just did foreplay and it went well.
Well, I think you should explain your birth control if he asks you to. Obviously at first you'll use condoms so he might not ask what your birth control is but if he feels it just say so.