Am I pregnant or having a chemical

Mo

My period was due last Thursday. Got first BFP at 9pm on Friday night. All of these are since Friday. I had bloodwork yesterday confirming pregnancy but my HCG was low at only 21. That worried me so I took another test at 10am today (pink dye) and it was negative. Got home and took a digital and it said “pregnant”. I’m on a rollercoaster....has anyone else experienced this and had it end positive? I’m worried that all of this points to a chemical or a pending miscarriage