You are not alone. Im trying to learn drawing too.
I’m a NewBe but this is what, I think…
I think you should learn human drawing first, the reason is this, learning anatomy drawing has nothing to do with anatomy and all to do with thinking patterns. as you are learning to draw a human you first deal with a major mental block and that is symbolic drawing, in your mind. I think the Idea is not to become a doctor but to over come that major mental block, as you learn more about drawing human anatomy the other kinds of drawings become much more manageable, because humans are the most difficult mental block to over come in drawing. When you move to animals I would guess you dont have to spend that much time because you have learned a thinking pattern that you can apply on them, I don’t mean they have the same anatomy, but you learn them much faster.
Now about feeling overwhelmed:
One thing from my other art learning experiences is good frustration management technique, at least this is what I like to call it is very important.
First thing is I dont judge my progress by looking at others, when you see anatomy drawing books you see a master at work and feel just overwhelmed. Judge your progress by looking at your previous drawings, then you start to feel much better. The idea is to get better at it one page at a time, and after few hundred pages you feel much better about your progress.
Second thing the Frustration Management, if you are frustrated use that to your advantage, frustration means your brain is trying to learn, so when you are frustrated that means you are about to learn something new and that is always a good thing, just watch your Frustration meter from time to time, and make sure its not turning against you, too much frustration is bad for your health.
Third Break things into manageable steps so you dont have an impossible task ahead of you. Dont go for your master piece at the start.
Fourth a good teacher or source is very important, because sometimes your brain just doesnt know what to do, I am using these videos for my source it’s great.
http://the-structure-of-man.blogspot.com/
and have a lot of fun doing it because, if you dont whats the point.
Thats how I deal with it, Hope that helps.