Scared!

I am 4 weeks 5 days and got my BFP at 4 weeks (used a digital as test strips were only faint). This morning I poas and it was negative and went to the clinic to poas with another negative. They sent me for blood work and I am 17ui/l. Is this still okay? Don't I need at least 20 to show up on a stick? Would that mean my levels have gone down? Just trying to prepare myself if this is not good news