pregnant or period?

I got the Skyla IUD implanted on May 18th, 2015 and haven't had a period since. About 3 weeks ago, I went to visit my boyfriend (long distance relationship) and we had sex without a condom about 12 times or so. He pulled out every time with the exception of twice. Now I am having sore tender breasts, light pink discharge, on and off cramps, and backaches. I also had strange grey pink tissue-like discharge this afternoon which I included a picture of. (Sorry if it's TMI) I'm not sure if this is a period coming on, my IUD causing trouble, or pregnancy. Any opinions??