Miscarriage or ?

So yesterday after I was bleeding for about 7 days which was very light by the way not normal for my period anyways when I went to the bathroom a huge blood clot comes out then about a hour later I start bleeding very bad like a waterfall I was nervous so I went to the doctor and they said I have a cyst but my boyfriend swear he think it was a miscarriage bcuz he claim his ex had one the same way but mine was like a murder scene. He only been home 3 weeks so he’s wondering why would I bleed so much if I was only three weeks can u even miscarriage at 3 weeks and the hospital claiming I have a cyst they never mentioned miscarriage help has anyone actually miscarriaged at 2 to 3 weeks with a extreme amount of blood