cramping and spotting on bcp

Hi ladies. I've been on bc pills three weeks now since I have an e ndo bio repeat Wednesday. I took doxycycline since my first e ndo biopsy revealed inflammation. So we are keeping me on bc pills until I test all clear and can prep for my FET. I never get my period on my own so it's weird for me to bleed without med help. Two days ago I had af cramps and some spotting..yesterday no cramps and no spotting but I had a glob of ewcm ..similar to when you've taken lots of estrogen if you know what I mean...then today cramps and spotting. Its just odd to me considering im on bc pills. Has this happened to anyone ?