Could I be pregnant with Mirena? Could there be something wrong?

Firstly, I think there is something wrong with my IUD. I've had it for 3 1/2 years, and from time to time I get these really bad, strange cramps. They aren't like the cramps I had when I had a period (pre-Mirena), they feel like they're coming from my IUD pushing into my uterus or something. I've had it checked only twice and last time they said everything was completely fine. My uterus curves forward, so I think maybe it just wasn't able to sit in there properly. I am looking into getting it taken out but I don't have any insurance right now and when I asked my gyn they wanted to charge me $250!!! But I am too afraid to take it out on my own.. and I know that I shouldn't anyway.

Second, I was reading several accounts of women who also have the Mirena, and became pregnant. A few who were able to leave the IUD in for the whole pregnancy and have perfectly healthy children. I was also reading that you can start to feel the baby anywhere between 8-15 weeks. Well, I thought I felt something last night. And I like to think I am very in tune with my body. I took a pregnancy test 30 mins ago and it showed negative (but I bought more to try just in case).

I have all the symptoms of pregnancy (without the sore breasts) and I am just curious if I could be. I know the best way to tell is to get a blood pregnancy test. I am just curious if it's possible... maybe I've just lost my cookies.