Help! Low HCG levels

Hello everyone!

I took a pregnancy test 2 days ago and it came out with a very faint line. I tested again yesterday and it came exactly the same. Today I tested again and the line was barely visible this time. I got really worried, so I got a blood test and my HCG levels are just 13mUI/ml. I will have another blood test in 2 days. But I'm already worried because I feel less symptoms today (less nausea, my breasts are less sensitive) and I imagine that if the test showed positive 2 days ago, my HCG levels in blood should be higher by this time, no? What do you think?

Does it mean I'm having a chemical or an ectopic pregnancy? I'm so sad and confused