False Negative?

A little back story, I’m 16, I’ve had the Skyla Iud since June 2018. This is my second missed period and I took two pregnancy tests. I took one last Friday that was three years expired and it gave me a negative with a very faint line. I have been feeling pregnant for a few weeks now.( I had unprotected sex on 1-4-19) i just took another test tonight because my lower abdomen has been feeling tight and I’ve been having light cramps by my hip bone on my left side. I’ve had pretty much all the normal symptoms up to now ( sore nips, frequent peeing, bloating, hungry all the time, and I’m always super tired(a couple weeks ago I had nausea but it subsided and the rest of the symptoms came)) I’m scared that I’m pregnant and can’t produce enough HcG for a test or somethings wrong that I keep getting false positives. Someone help me figure this out please