Today I'm 10-11 DPO. Implantation or period?

I started spotting yesterday morning. Dark brown spotting, really light spotting I notice it only when I whipe! Usually my period is verry, verry heavy. I had a D&C a month ago with almost no bleeding. I ovulated 2 weeks later and we forgot to use condoms. (I know it was really stupid of us). Now I started to have nipple pain, I'm exausted non stop, and suden nausea all thru the day! I took a couple of pregnancy test but they came out faint positive. I know it can be from my miscarriage but again maybe not? What do you guys think? Any of you went thru something similar?