Please someone help me!!!

So I've got checked , ultrasound tablets everything and nothing has worked or came back negative at all , I've had my periods since the 1st of July and still have them, they are heavy as hell, the periods will go different colours like spotting, to brown then back to red with like black stringy stuff I don't know if it's blood clots or not but they have recently been really red with the black stringy stuff when I wipe myself.. It's never happened to me before, but before I got my periods , I missed my periods for 2 months and usually I'm regular every month on time? I'm sexually active and not on no conception. Could this happened from a miscarriage or would I have known ?? I'm so confused and need advice ASAP ladies 😣😣