Started my period even though i finished few days ago

I’m 16 and in high school (UK). Last year I had sex which was one of the worst decisions I made in my life and obviously it turned into a situation where my mum found out i was going to be forced to do FGM (my parents go to court for this) constantly abused, and i still am by my parents. But that doesn’t matter. When I got checked out at the health clinic they suggested contraception incase I have sex again (I haven’t had sex since then) but I did the injection contraception where my period stops. However, I did it in april and was on my period until January, itdidnt stop, so i told them i don’t want it anymore and in January it finally did stop, yay! Now, I had my regular period which ended just a few days ago., I get migraines and my GP gave me pills to take when I get them. However, yesterday in school I was feeling terrible at my worst! I had reallyyyyy bad back pains, i couldn’t move my legs, my headache was sooooo bad at its worst i even took my medication and it didn’t help at all, i vomited in the school toilets, and my school immediately sent me home, i didn’t eat at all and i am still feeling terrible. However, this morning I woke up and I still have the same symptoms as yesterday but not as bad, however I got reallyyyy bad cramps now and i’m on my period! Wtf?!!! Is this because of the contraception? I’m going GP but i can’t tell them i’m on my period because my mum will assume things and i don’t want my mum or the GP to find out I was on contraception because they might tell my mum that’s the reason and my mum will literally kill me! I don’t know what to do. Someone help me pleaseee! Thank you❤️ Please no hate I know i’m young and what I did was the worst decision i’ve made in my life.