Someone please read!

So I tested positive the 19th of August 4 days after my period ended. I called my OB they got me an appointment for three weeks later and told me I was pregnant from July at least the receptionist did because she says there is no way I would have gotten a positive anyways, fast forward 3 weeks, I am 5 days late on my period it is always on time I’ve never had a late period, when I say on time it’s every morning when it is expected to come with my first urine of the day. my boobs are sore and nipples hurt. My back aches, I went to the ob today and there was no sac, no baby. When I spoke to the doctor she told me If anything I was only 4 weeks because my period came for the month of August. So they took blood work today and I go back Wednesday for more, results Thursday. Has this happened to anyone? I am so upset and terrified I might not have a baby.