Help?!? Miscarrying?

I am 4 weeks pregnant. I started bleeding last night not a lot but it was a bright red. I went to the hospital to get checked out. My beta levels are 80 which is low but also not uncommon for so early in a pregnancy. (I still haven't missed my period so I am super early). They did an ultra sound and there was no gestational sac visible which they also said is not uncommon being I am so early. But with the two of those factors combined I could be miscarrying. I won't know until Tuesday when I get more blood work done to see if my levels are doubling as they should. Anyone else experience this?? Thoughts/comments... could I be miscarrying??