Beta HCG

I went to the ER to rule out an UTI which I did end up having, just for them to give me no medications but tell me I’m possibly pregnant! mind you I’m so confused I just got my IUD remove on September 1st and had been trying to get it reinserted with no luck! The crazy part is I was just at the Dr Friday and she said nothing I just recently took a pregnancy test that expensive ass clear blue and it was negative just to find out Sunday I supposedly am?? I’m no familiar with Beta HCg so if anyone could fill me & inform me of it mines was 87