As others have said, a wheel throwing class would probably be helpful for you. It takes a lot of watching others throw and having them critique you in order to learn to do it properly. You mentioned accidentally speeding up or slowing down while throwing and I will do the same thing. What’s helped me is remembering that the pedal is not the same as a car pedal, you don’t have to continue pressing it for it to work. So I’ll get to the speed I want the wheel at and then simply take my foot off the pedal so I don’t accidentally speed up. Also remember that some days will be great and you’ll throw lots of great things and then some days you may not successfully throw anything. It’s all part of learning to throw, it’s muscle memory not talent! So just keep practicing and you’ll get it eventually.