I didn’t know I was pregnant????

What are the chances that I could be pregnant and have no idea or any symptoms??? The first day of my last period was September 21st, but my periods have never been regular. I’m not actively trying to get pregnant either I’d rather not be but whatever happens happens, I’m single but I’ve been having unprotected sex since then with one person, who I just found out has been cheating on his girlfriend with me. But I’ve been losing lots of weight and now it looks like I’m getting bigger and around my belly button feels firmer than normal. I don’t have any tests right now I have to get one tomorrow but I’m praying to god I’m not