Faint Line

My question isn’t necessarily do you see a faint line because I am sure it’s there. My question is how long does it take to get darker? I tested two days ago and got my first positive. It wasn’t fmu so I waited two more days (so the hcg had time to double) and used fmu this morning. I still have just a faint line. Wondering how long others took to get that blazing positive?

I took First Response test and got a better line but it still makes me nervous these ones aren’t darker.