I'm going to blow your mind and suggest that you stop sketching, at least sketching the way you have been doing it. I think your problem is that you're sketching a lot but you're not getting anything out of it. It's quantity over quality. Filling sketchbooks means nothing if you aren't learning. Your hand-eye coordination may get better but you're also getting better at making the same mistakes.
When you sketch, do it with a purpose. Try to learn one new thing every time. If you're unfamiliar with something, give it a go. Don't worry so much about being able to post a lot of drawings per week. The most important thing is to learn. Those who are good at drawing may sketch a lot, but that's not the key to success.
"Astronomy offers an aesthetic indulgence not duplicated in any other field. This is not an academic or hypothetical attraction and should require no apologies, for the beauty to be found in the skies has been universally appreciated for unrecorded centuries."