Implantation bleeding? Help!

The first day of my last period was 1/5/2015. My ovulation date supposedly was 1/20/15. I had unprotected sex 1/18/15. I'm suppose to start my period on Feb 3 (in 2 days) however, last night I started bleeding (I've never gotten my period early. I've also been tracking for 3 months. Last month was a day late but never early). Enough to require a light pad. Its more than spotting but not as heavy as the first day of my period. I took a test yesterday morning and got a BFN (this was before I started bleeding). Throughout the night last night I had to get up to pee at least 3 times & I also have some diarrhea (think that may be related to the cramps). I know I have to wait to see how long the bleeding will last but does anyone have any meaningful insight in the mean time? When could/should I test?