Possible Miscarriage, but so confused

I started spotting at 7 weeks, which was on a Saturday. I called my doc and she said if it gets to be red you should go to ER. It started to get red so I went in. There was a sac measuring only 6 weeks, and the ER doc said he saw a baby on the trans vag ultrasound but no HB. My hcg levels came back to be 5038. Of course the red spotting stopped, and I was back to brownish spotting only when I wiped. We went home confused with still no answers. He just said "it could still be too early to tell". Fast forward to Wednesday when my first u/s was originally scheduled, she said she saw just what appeared to be a sac and no baby. She said I'm thinking you are miscarrying and your spotting will start to increase over the weekend, but we will also draw HcG levels to confirm they are dropping. The next day, Thursday, they called me and said my HcG levels went up to 6853! What?!? She said because the u/s doesn't match those levels she thinks I will start to bleed and cramp more over the weekend. I still have had no cramps through all this and only spotting when I pee, nothing on my pad. I have passed some more tissue and it's gotten red since my exam on Wednesday, but why are my levels going up? I thought this was over.