I was at about 50-60 with a horrible 2 finger style on qwerty, now im at about 80-100 on colemak, and i can switch back to qwerty no problem.
That being said, I wouldn't recommend actually switching. It makes me incompatible with the rest of the world.
Work on transcribing your notes from your notebook into a digital notebook. Doesn't matter if you keep them, it's the act of typing that you want to practice. One of the biggest improvements I saw was when doing something like this (though transcribing for professors, not for myself). I was already a decent typist at that point, but having to keep my eyes on the text while typing (and not on the screen or keyboard) improved my skills significantly.
Don't put the text behind or beside the keyboard. Put it to the side and up. Get a small stand (like the stands for cookbooks) and set that beside your computer, next to the monitor. Your keyboard will still be in sight, but keep your eyes focused on the text instead.
Then practice. Practice doesn't have to be a typing course; it can be something you want to do anyway - programming, transcription, writing. For me it was chat rooms as a kid. The more you practice, the more fluent you'll get.
Again, to be a fluent typist, you don't have to be a perfect touch typist. The important thing is not to be hunting and pecking. It's ok to develop your own style that uses different fingers than the recommended ones to hit specific keys (everyone's hands are different after all) or to look down at the keyboard now and again to reorient yourself.
But it sounds like what you need to do more of is practice.
I now try to use key bindings everywhere and minimize mouse usage. I’m way less mouse oriented than before and I’m more productive. I know I have a ways to go still. And I like that challenge.
I know you mentioned you are not a developer. For those that are/would like to be, this may be helpful.
Cover your hands with a piece of cloth while playing for maximum improvement.
I'm unsure how good it is now, but I used this years ago. Free, ran through a lot of standard typing exercises. It was very helpful in moving me from "proficient with Dvorak" to "filling the keyboard buffer with Dvorak". It should be similarly effective for QWERTY and other layouts. Actually, I think I used the QWERTY exercises with the Dvorak layout.