Pregnant?!

I have the IUD (Mirena) inserted 4 months ago. Last month (07-28) I had sex and for the first time my boyfriend came inside once and then 2 weeks later he came inside again twice. Since the first week of this month I've been feeling sick. I've been having nausea every time I wake up in the morning or every time that I smell any kind of food. Even when I have a nap in the afternoon sometimes I feel nauseous. That happens too when I finish eating something.

Every now and then I get a couple headaches, backaches and at the beginning of this week I had pain in like the ovaries (I don't know how to explain) but it was definitely something weird because it was below my belly button and above my vagina. It felt awful.

I am worried because this has never happened to me.