Post prangency test negative at 3week +

Hello Doctor, I am 17 and need confidential advice. I had sex on May 23rd and took an i-Pill within 28 hours. On June 13th (my expected period date), I had a 3-day bright red bleed with small tissue fragments/clots, mostly when wiping. On June 16th (3 weeks and 3 days post-sex), I took a home pregnancy test and it was completely negative. I have no pregnancy symptoms and a flat stomach. However, I have had continuous light, on-and-off spotting from June 13th until today (June 27th). The spotting increases slightly with clear/milky discharge during sexual arousal or after an orgasm, which also causes a temporary 5-minute lower abdominal muscle cramp. Today, after drinking heavy sesame juice, my stomach felt hot/burning and I had a brief gush of brown/red fluid which has now stopped. Can you please advise me on how to stop this 14-day spotting? Would a short course of progestin or daily birth control pills help regulate my cycle? Thank you."