3BFP!! Then a Negative at Drs?!

Christina
So I had been spotting for 3 days. At the time not sure if implantation bleeding or not. I was at 40 cycle day and the started what looked to be actual period. I took a HPT and got a positive. In shock I went to the store and bought another brand and came home and also got a BFP! So the next morning I'm still bleeding so just to be sure I take the other test and it was a BFP as well. Being that I was bleeding like my period I went to see a OBGYN  that evening and their urine test came back negative?! And as I was concerned it appears I had a miscarriage.  :( however the doctor said I could retest at home in a few days just in case theirs was wrong. Has this ever happened to anyone else? Is there even reason to take another test in a few days? Thanks!