Miscarriage?

I found out I was pregnant 8 days ago. I took many hpt and they all came out positive. So excited but I was terrified of having a mc. I missed my period on Saturday and was feeling awesome! This morning I had sex- didn't know I wasn't supposed to... And I had brown discharge right after sex. Later today around 4, I went to the bathroom and wiped and there was a fair amount of fresh blood. I called the doctor and made an appt for blood work, but I'm afraid I'm having a miscarry. All I can think about is whether or not I'm cramping. I can't tell. My flow isn't overly heavy, I have passed a few small clots, but a lot of stringy mucous. Am I having a miscarriage?? Please help!