I have a friend that was once in a similar as you. She slowly self taught/re-learned most of the concepts that was taught in high school and passed the entrance exam for her college for a Bachelors in Accounting. If you're interested, perhaps invest ~2-4 hours after work everyday to brush up on the subjects you've struggled with and overtime you'll be able to enroll in a program that opens you up for better paying jobs.
Best of luck to you and I hope my comment helps you out!
P.S. A good place to start for her was
https://www.studypug.com/