Miscarriage!

This is my first pregnancy and I had surgery to freeze a cyst on my ovary and im 4 weeks pregnant and doctors said everything should be fine with the baby well yesterday morning I got a clump of blood in my panties went to the emergency room and they said that my hcg levels are the same as they were on my day of surgery and they couldn't find the sac in my uterus so today I'm having horrible cramps and period like bleeding with clots doctor said it could be from my surgery but I know Im having a miscarriage .