Is this normal after taking plan b??

My last period ended on the 11th of July. Had unprotected sex on the 17th and took a PlanB on the 18th. We both weren’t sure if he came but we took one because we were scared and to be safe. My next period wasn’t supposed to come until the 7th of August but I got my period two weeks prior - so one week after taking plan b. I got my period like normal and then it got lighter and darker with brown stringy discharge and then it got heavier again as of 08/04

Can anyone tell me what’s going on and why is my period lasting a long time? Is this due to the Plan B or should I go to the doctor? I am worried.