Miscarriage or not?!

I should be 8 weeks pregnant tomorrow and have my first check up on Tuesday with the Midwife. Today I've had to go to A&E as I've had cramps and passing a medium amount of blood with tiny clots and one big clot just slightly bigger than a 50p piece. I've had tests done but doctor's can't tell me anything for sure until tests come back. I've been given MicroBID antibiotics incase it could be an infection to rule that out. The hospital has booked me in for an early ultrasound on Wednesday morning to check. Ive taken a pregnancy test at home tonight and it's came up negative. I'm already mourning my loss as I feel in myself it could be a miscarriage but has anyone else had this and continued to be pregnant or have a healthy baby? It's my first pregnancy and just feel like I need some more advice than I'm getting now.