What's wrong with me?

I got my depo shot late (which was almost 2 months ago been on the shot for a year now ) and I had to use a different method of protection.  Which I didn't and two weeks after that I started feeling pregnant symptoms decided to take a test 2 weeks after the unprotected sex. Which came out negative. So I gave it a rest. My period is irregular so after almost 2 months I am spotting but I have abdominal pain on one side and under my boobs area. The pain comes and goes Also sometimes itfeel uncomfortable when I lay on my stomach. My friends are telling me to take a blood test but I feel like it's going to come out negative. I don't have my next shot appointment until January 26 so I don't know if I should be worried to make one sooner. Has anyone experienced this before?