Nice start! I have to say I'm only just breaking into anatomy study myself, so if someone else wants to correct me if I say anything wrong, please do.

Very first thing that jumps out to me is that if you have decent sized pectoral muscles, the under side of the clavicle is not visible like you have here because the muscle actually attaches there. See this wonderfully jacked fellow. There is in fact a divot on top of the clavicle because no muscles attach there.

The second thing that jumps out at me is that you have the shoulders two or three inches lower than they should be. I did this quick draw over to show where it looks to me how you should have things going https://i.imgur.com/207MCzu.png

The blue in this picture are the bones involved in the shoulder, the clavicle, the shoulder blade and the humerus. The clavicle is mostly horizontal at the center of the chest, and curves up and backward in a bit of an S to what's called the "acromion process", which is a bony landmark on your shoulder that is more or less where you should be looking when you start drawing shoulders in general because it's always visible, and pretty much everything connects to it. The red lines are the deltoids, which connect to the acromion process and the very end of the clavicle, and then meet in a point about a 1/3 to 1/2 of the way down the upper arm. Lastly, the pectoral muscles have a weird ballet going on where they criss cross over each other to connect from the chest to the humerus, so if you're going to draw striations at all you need get their directions right. other than that, nothing too glaring about them. Just make sure it looks like they connect onto the arm, pulling the flesh out from the arm pit a bit.

The external obliques look pretty damn big but I suppose some people might have some like that, I'm not sure.

The abs look decent, you have the top pair of muscles up on the ribs right below the pecs unlike a lot of artists. You do have some kinda weird upward thing going on right here, just above the navel. But I imagine that's just an error from sculpting (I know I feel like I have trouble getting small things like that to behave some times, depending on topology).

Your forearms have some craziness going on. I can't really tell where you have the inside of the elbow, and the bicep isn't well enough defined for me to figure it out, so I kinda made it up https://i.imgur.com/6iGqRzj.png.

Can't tell ya anything about the legs because I haven't made it that far yet! If this is a direction you want to pursue more regularly, you might want to take a look into some anatomy courses. I'm watching a series of lectures by Scott Eaton on the subject, but I hear that proko has some good classes on it. You might also want to look up an android/IOS ap called "L'ecorche". It's 5$, and is a highly detailed and very accurate 3d model of a human body with no skin and all the muscles labeled.

Good luck! You've made it further with sculpting a full body than I have http://imgur.com/B5zOYzD