On April 10th And 11th My Husband And I Had

On April 10th and 11th my husband and I had unprotected sex at least 4 or 5 times. On the Tuesday the 14th my mirena just came out. I know that if you have sex with in 7 days of the mirena coming out that you can get pregnant. (on mirena web site) On Friday the 17th I started to spot. I put on a pantie liner and by late Friday night there was very little blood on it. I spotted thru Sunday the 19th. With very little blood. This was nothing like a period not enough blood and the color was more brown most of the time. Also everywhere that I have read women say that they had very heavy bleeding with lots of large clots after the mirena. I know a lot of people say that most women don't have implantation bleeding but it did with my daughter who is now two, but it was just a very pale pink discharge. I have been having headaches, lower back pain, and discomfort in my stomach. Does it sound like the spotting was implantation or from the mirena?