A little confused

Gabrielle
I took a hpt last week. It was slightly positive. So I thought "okay, yeah I'm pregnant." I went to my ob on Thursday. Took both urine and blood tests, both were negative. So I thought " okay I'm not pregnant, I'm relieved." I'm only 20 as of last week. I'm not really ready for a kid. But I was due for AF yesterday and it never showed. I didn't panick just yet because although I'm always on time, I sometimes be a day late at the most. But today is the same as yesterday. No AF. I still feel pregnant. I don't know what I should do. I have heard of pregnant women with little to no hcg but that's rare, right? Should I go and ask for an ultrasound scan or just wait it out? And should I still take the prenatals just in case? Please let me know!