I had sex with my BF a week and a half ago during sex I bleed as though it was a period only that day. My period was due 2 days ago and I am late I am almost 45 years old. What do youthink?

I think that you had sex and it's possible that you could be pregnant, or it's possible that you're just late. OR maybe you're starting menopause. Either way there's no real way to get a definite answer over the internet, so talk to your doctor or take a pregnancy test, those are the only way you'll know for sure.