Suggest Remedy For Periods Problem

Hey there! So I m having a minor freak out. I am 19 years old, and am currently taking an oral contraceptive called Sprintec. I ve been on it for 4 months. I am sexually active.March and April were both normal periods, and I had no problems or side affects when on the pill.On the first day of my May menstrual cycle, I noticed a light pink, tissue-like clump in my period blood. I was experiencing mildly severe cramps. The blood was a thick brown for two days, and then became very heavy, and carried out like a normal period. I had assumed it was a miscarriage, because I believe I had missed a pill, but I didn t seek medical help.My June period was back to normal, and I, again, had no issues.I just received my July period this afternoon, and I had normal cramping for 20 minutes. Then I had absolutely no cramping for the rest of the day, which was unusual. When I went to change my pad, I noticed a larger clump of the same consistency as my May period, with the same thick brown blood. My boyfriend and I have not had sex since May, because we are now extra cautious, but we are now concerned that this keeps happening. It is late, and I am planning on going to the doctor s to get checked out, but I would like to know if you have any answers for me. Thank you so much!