Cramping at night and low hcg levels

Hi all, This is my first pregnancy and I am apx 4 weeks, my last MP was oct 10th. My doctor ran a blood test on the 1st and i was at hcg level 17. then on sunday the 6th i went to the ER because i was experiencing heavy cramping, the cramping only comes on a night and I have no bleeding or spotting, just really intense cramps that last until i either vomit or have a bowel movement. At the ER they took my hcg levels and they were at 250. I went today for my prenatal apt with my family doctor and he was telling me that it could be a miscarriage and that its just to early to tell. I'm a little freaked out because I am still cramping and my hcg level 2 days ago was pretty low (250). Has anyone else experienced this? and does it sound like the signs of a miscarriage? I know the hcg levels are suppose to double which mine have 17 to 250 in 6 days but the numbers are pretty low, and combined with the cramping it really worries me. any help with this ladies would be amazing, I've always wanted to be a mother and I'm so excited to have this chance but cant stop thinking numbers and miscarriages, someone help me!!