I’m worried

I’m on cycle day 38, and my period is 5 days late. I’m known to have irregular periods. Well, last night, I had sexual intercourse after a party, and I was wondering if there was a chance I could get pregnant. I really don’t want to tell my mom about this, because she will be highly disappointed in me, and I don’t really want a baby right now. I know I made a mistake, but I honestly need advice because if there is a chance I suppose I’ll have to talk to my mother about this and how we can sort this out. I know for a fact that he had came inside me, and I was on my back. (I’ve been reading about this a lot, and apparently being on your back while the male has ejaculated, could increase fertilization of the egg). But since I have irregular periods, I’m unable to to detect if I’m ovulating. I’ve had slippery/sticky discharge randomly these past couple days, so I don’t know if that could be a sign of ovulation or if it’s just normal discharge. I’m honestly so stressed and I need help.