I want to know the best way to raise my credit score!

Pretty much what the title says. My credit is 550 and it’s putting a huge burden on me now that I’m married. My husband has superb credit but it still doesn’t sit well with me that if anything were to ever happen I couldn’t rent or even get a good car in my name. The reason my credit is so bad is due to past medical bills. I have about 3k in debt to medical and I’m not even sure if paying them off is going to help. I do have student loans but I’ve been paying them off on time with no problem, and I’m currently going back to school. I know that I can open a secured card and help raise it that way, but is that my only option? Is there any other way to raise it? I really want to be out of debt as soon as possible.