I am going to make a suggestion. Try speaking with the head of a math department at a local community college or at the nearest college. Explain what your goals are and ask for guidence in putting together a plan. I think you will be suprised. You may well find a mentor who can help you. Everyone learns at their own speed and many aren't ready for some subjects until later in life. For example, I was a C student in high school and college in chemistry despite the attempts of my teachers to get me interested. In my 40's all that learning that I didn't care about started to surface and I found that I now remembered and understood more than I actually thought I learned. The same thing happended with Calculus. I barely passed it but when I needed it for my work it became fascinating. I believe you are about to experience the same sort of revelation. I am in my 60's and I can't wait to learn new things. A completely different person than who I was when I was younger. Become curious, it will lead you to a life of wonderful fullfillment.