Ok, this might not sound good, but have you ever thought that he's just enjoying you giving him a blowjob all the time, and he's preferring to do that instead? I'd say stop doing that for him and see how much he wants to try actual intercourse. Men can fake ejacualations as well, or it could be pre-cum your noticing. Also, for my interest, would you answer how you have oral sex when you are on your period? Do you use a tampon inserted or something?