Please Help!

Okay I'm ttc and I tested positive on four hpt the lines were faint but there. I posted on glow and other ladies confirmed it. I had a blood draw that was negative then Monday I spotted alittle Tuesday it was alittle heavier and Wednesday I stopped abruptly. I went to the bathroom and when I wiped there was nothing. There was no gradually reduction in blood it just stopped. So I had a period for 1 day?? Still having pregnancy symptoms nausea, vomiting, tiredness and so forth. I don't know if I'm pregnant or not. If I'm not what's going on. If I am why was the blood test negative? Please help!