Firstly, good for you that you’re continuing to learn and not give up.
I, for years, played exclusively with my fingers until I discovered the Black Mountain thumb picks. (https://blackmountainpicks.com)
They are rather expensive, however they fit perfectly on the thumb and give me the possibility of strumming and finger-picking without having to do hybrid picking which I find is a pain.
After I got used to the Black Mountain thumb picks, I actually found that I could also play with a regular flat pick, especially after I put on them Monster Grips silicon grips (https://www.monstergrips.com) which keep the pick from slipping and falling off your hand. There are times that I prefer a flat pick to a thumb pick, particular if I’m playing solos over a backing track for example.
Besides that, there are different methods for holding the flat pick. I tried different ones, till I found the one that works best for me. Check them out.
I hope that helps some. Lots of luck.