Line get darker?

I found out I was pregnant Tuesday night around 10:30pm. pregnancy was confirmed the next morning at 10am through a blood test. I have been taking a test every morning & night since. I have probably taken too many. This is my third pregnancy. I have one baby earth side. So pregnancy is very scary for me. I lost my first child early on in pregnancy & I was high risk with my second pregnancy. I am very early, I’m thinking right at 4 weeks. My lines aren’t getting darker so far, I know your HCG levels are suppose to double every few days. I’m a nervous wreck. When should my HCG levels double? Here are a picture of all test I’ve taken so far.