what happened? is this because of plan b?

Carly
So, let me start by saying I took Plan B on January 20th because my boyfriend and I had unprotected sex. After this, I still got my period as I usually did at the end of the month. It lasted around 5 days. Then, around February 16th I was feeling strange, I had allergies and was cramping and my body ached and I felt like I was getting my period early. I saw signs of spotting so I used one tampon before realizing my flow was too light for it. So I discontinued with them and spotted on and off. I took allergy and cold medications. My mom got concerned that I might be pregnant because she had some of the same symptoms before, so I took a test with a clear "Yes +" answer. I kept having cramps and had some pinkish discharge for days. I was freaked out, my world turned upside down and decided I needed an abortion. Upon going to the clinic, they gave me an ultrasound in which they saw nothing and tested my urine and it came back negative. I'm still spotting today (a more regular blood kind of spotting) and it's now March 13th. What is going on with my body? Can anyone relate?? Any advice appreciated!