Help!!

So I finished my period March 2nd and had protected sex March 3rd. We fooled around prior to the actual intercourse but there was no unprotected sex going on. We stopped the sex and I finished him another way and he ejaculated onto my bottom (not sure if any cum was to have gotten in my crack) This occurred around 10pm on March 3rd and I took an emergency contraceptive on the following Tuesday around 1pm (making sure I made it before 72 hours). 2 days ago (March 11th or 12th) I started bleeding, it was brown/reddish and today is just brown spotting a little. I am currently on the 3rd day of my ovulation week according to eve. Is there a chance I could be pregnant and this is implantation bleeding or am I just experiencing side effects?