Hello and welcome to the forum. Conception happens typically very near to when you had intercourse. Sperm lives up to a week. If you had intercourse 8 months ago, you would be soon to deliver a baby if you became pregnant from that incident. So, it is really not likely. I guess there are documented cases of a woman being pregnant and not knowing it but it would be very rare and you'd be almost to term at this point. Periods can be late for any woman at any time. Things as simple as additional stress can cause you to be late. If you've been sick. Etc. Anything like that going on recently? They also can just be late for no real reason. Just a fluctuation of the hormones. We wish you the best.