Confused. Please help.

So last week I went to the doctor and did blood work and it came back positive for being pregnant. I took multiple hpt that came up positive within the 3 minute window as well... Well I started having heaving bleeding on Monday and they had me go yesterday for more blood work and now today they are telling me I was possibly never pregnant?? Has this happened to anyone else? I don’t understand what’s going on? How can they tell me I’m pregnant then the next say I never was?