For the reverse squats, make sure your knees aren't coming out past your toes. Also don't come down as far if it bothers your knees. It's okay to make the squat smaller- same with the sumo squat. Don't come down as far, and also make sure your toes are turned out and your back is straight.
If none of those things help, it's okay to do other exercises instead. You don't want to push yourself and end up injured.
Hope that helps a little!
"You may have a fresh start any moment you choose, for this thing that we call "failure" is not the falling down but the staying down." Mary Pickford
"No matter how slow you go, you are still lapping everybody on the couch."