Implantation bleeding or period? Please help!

Hi! I had unprotected sex on the 8th day of my cycle and thought it would be safe, since I wasn't near my fertile window. My cycle is regular, from 28-30 days. I had protected sex using condoms the rest of the month but started developing classic pregnancy symptoms: nausea, cramps, headaches, mood swings, dizziness, taste disturbances, breast growth etc. Yesterday (cycle day 30) I noticed a small drop of bloody cervical mucus on my underwear, and today I have a heavier flow of light brown blood. I'm going to take a pregnancy test tomorrow morning just to be sure, but I'd like to hear experiences from other women regarding implantation bleeding/possible pregnancy. I read that it's not likely that this is IB because I had unprotected sex over two weeks ago and the two pregnancy tests I took last week and the week before were negative. Any advice or info is greatly appreciated! I wasn't able to find much reliable info using Google.