On Depo Shot, Had Unprotected Sex, Painful Sex, Dark Circles Around Nipples, Negative Pregnancy Test. Pregnant?

Hello, I have been on the depo shot for a year and one month. I have always had unprotected sex and he has never pulled out. I was only late for my second shot (out of four) and I was tested by the doctor and it was negative. I have not been sexually active from the beginning of June until August 16th. I recieved my shot the 19th of July. I ve had sex 3 times and I spotted a couple days after which has never happened before. It does hurt a bit to have sex. I just noticed I have dark circles around my nipples but he has been grabbing them very hard so could this cause it? I also have some breaking of the skin (well like little red dots) on my breast which I m guessing is because he grabbed them too hard. It s been about 12 days since I had unprotected sex the first time (well since I started again) and I took a pregnancy test and it came out negative. Did I take it too early? Do I sound pregnant? I have not got a period in a very long time, maybe around 6 months. Not much spotting either, until recently.