How to be sure it was a miscarriage even if I never knew I was pregnant?

I think I had a miscarriage but I'm not sure. I never even knew I was pregnant. If I had a miscarriage I'd be in the 1-2nd month. My symptoms- Last month I only had a light 2 day period (Didn't think anything of it) Black dark blood came out in clumps. But not very heavily bleeding. HORRIBLE pain. I've never had pain like this. If I was laying on the bed and anybody moved I felt like I was going to die. I couldn't even have the blanket over me because it was too much. Someone Else's touch just made me want to die. The smell of food made me sick. My hips hurt. My lower back hurt. It was just cramping. Normally I'll cramp for a few seconds or minutes and it'll come and go but this time it was constant pain. My periods are really irregular so I can't say if it's around my normal time of the month because I don't have a normal time. This was the worst pain I had ever felt in my entire life. My whole pelvic area was just in hell. But how can I be for SURE it was or wasn't a miscarriage. Could doctors do a sonogram and know if I had one even this early in pregnancy?