Could I really be 8 months pregnant?

In February, around the time of ovulation, I had sex with a guy friend and the condoms slipped. My period in feb was very light but still lasted the 5/6 days I’m used to. Since then my periods have been very light but long, a drastic change from my long and heavy periods I have been used to. I have taken multiple pregnancy tests, all negative, even digital ones say negative.

In May I had an ultrasound to check for fluid in my abdomen after a bad fall and asked them to check for pregnancy just in case, they did and said they couldn’t see any in uterine pregnancy but did say my endometrial lining was quite thin, I would have been 14 weeks by that point.

Since then my periods have got slightly heavier with quite bad cramps right up until this period which is missing. I am very late now and thinking “what if they kissed something?”. I know now, considering the timeframe, I would be 8 months pregnant.

I have not put weight on, if anything I’ve lost a few pounds, none of my clothes feel tighter, and I have cyclical breast pain in line with my periods coming and going. Anyone got any clues?