Pregnant?

Hi, I have a question and wonder if anyone here has experience with this. I missed my pill for one day and then just continued the next day, but suddenly I got my period for 3 weeks. A lot of bleeding stopped 3 days after I started my period, and I also stopped taking the pill. I had to pee constantly. When my period was over, I got a lot of dizzy spells. Now my belly is starting to swell, I feel nauseous, can't get a bite down, am constantly tired and exhausted, and wonder if I'm pregnant. A few friends think I had an early miscarriage, but I find it crazy that I'd be pregnant and why my belly is swelling so much. I'm going to the doctor tomorrow, but I'm freaking out right now and would like to know if anyone has any idea.

Greetings