I don't mean to sound insulting, because what I am saying is true for me. Me being in a gym without guidance is like giving a 4 year old a gun. Somebody just might get hurt.
It sounds like you may have tried to do too much, too soon. Have you thought about enrolling with a physical trainer?
For my example, the place I did Physical therapy at is also a membership gym as well. They had a program where you could transition over. That program was a couple of years ago, but I paid $165 and ended up getting 18 personal sessions with a trainer, and when I joined the gym, my membership enrollment fee was waived. I've also learned how to use a lot of the equipment safely and not over-do it.
You will do fine. Don't give up.