Trying to fix my credit

I’m working to repair my credit that I messed up when I was 18, now 24 and thought I was doing good. Been on CreditKarma for over a year keeping track of everything and thought I was doing good. I got an opensky secured credit card 5 months ago and I’ve been making all my payments on time, as well as a secured loan. My score went from a 550 to 660 on CreditKarma, I applied for an Amazon Store card today and was immediately declined. Irritated I signed up for myfico’s score watch and found out my FICOs are all ~550….. not thrilled.