Confused!

Tq

I had a loss at 18weeks on June 10th ...got my first period July 9th ... past couple days I've been getting faint lines but I went to the ER and they told me my blood levels are low and I am not pregnant... I can't figure out why I keep getting all positives on Walmart .88 brands (can't count how many i took) .. I went and bought another brand and I think I see a little something..I am now on cd 19. I believe i ovulated on 7/23 but not sure because I thought I had a surge before that on 7/18.. I'm just so confused .. I guess only thing to do is to wait..