Am I pregnant now? Or what could be wrong?

Hi everyone!
I need your help. I'm 17 and have been on the pill for 3 years, so I have a 28-day cycle. Usually, my period starts 2 days after I finish the last pill. This time, I was 4 days late. I got my period on Friday, but it's not like usual... now it's been 2 days and it's almost over, while normally I always have it for 6-7 days. Does anyone have advice?
Before that, I had some nausea, sore breasts, headaches, and pain in the womb area. I thought the nausea was linked to an iron deficiency I had, but that's been resolved, as the doctor already told me. I'm supposed to go on Wednesday to go over everything.

Thanks in advance!!