My dr put me on birth

control about 6 weeks ago. Before I started them my breasts got really sore and I spotted a few days before my period. But I didn’t think much of it and started the pick on that Sunday. Well throughout the month my breast continued to be super sensitive which I assumed was from the pill since it messes with hormones. Well the past couple days I started spotting then light bleeding which I read can happen the first 3 months on the pill. All day I’ve had cramps and bad back aches/ I started bleeding heavier and a huge clot came out. It looks like a sac and is thick. Is this a possible miscarriage??