Okay I'm new to all this, never did very much sex ed and my mum never explained any of this properly to me, I only know what I have learned from googling.Saturday night I had unprotected sex. Just a one night stand. Didn't get his name so I have no way to contact him. Feel free to judge, because I know there are people who will anyway.Anyway, on Monday I woke up with a stuffy nose and a mild headache. On tuesday I woke up with my nose 10X worse, and I was also having mild cramps and I was tired all day. And today (wednesday) I got a reddish-brown stain in my underwear. I know it seems unlikely, is it possible that it could be implantation bleeding?I also have an irregular cycle. Never had a normal one. I can go up to 8 months with no period, and then I get a heavy 2 week period. So I can't give you any dates for cycles or anything.But any advice or anything is greatly appreciated! Thankyou