What is it ? please help!

i’d love if anyone can please tell me anything about this problem i’m having. so for as long as i can remember my period has always been on time and once a month. for a few months now i’m always bleeding after my periods and it’s some spotting and noticed it’s only when i ovulate. i went to the drs and they told me i had a cyst and that it had erupted but i also had thick uterus lining. that was last week. this last period was from the 9-14 and i ovulate this week according to the apps. last week (right after my period) i took a plan b on thursday and then last night i had pain and i started spotting but this morning i had a lot of blood and i still do every time i use the restroom. im so scared and don’t know what it can be. i don’t know if it’s related to what my dr told me or the plan b? but plan b wouldn’t make me bleed this much right ? i don’t know if to go to the er or if it’s just the pill 😭😭