Your fine mate, just practice a little more if you think you're slipping.

That's impossible, it may look like it for a bit, but it isn't regression it's progress. Either way, if you stop, that's a sure way of not getting better, if you continue drawing it's impossible that you don't improve. When I compose or even play the piano, I always think that I'm getting worse, but then after playing a piece badly four times, or composing five pieces of crap, then I get something nice (to me at least), sometimes I play/compose things that I think are horrible, but others like them. Really, you cannot let these doubts affect you, it's just your mind playing tricks on you.

You're fine. What's happening, is that you're drawing the same, but your standards are raising faster then your skill. That means your improving. :) You're seeing more and more mistakes, over thinking them, and trying to hard to correct them and in turn, it's draining more of your energy so the rest of the picture starts to look shabbier and shabbier to your own standards. In reality, it's only making you a better and better artist, so don't fret! =3

Chaos is correct. People do sometimes regress, but I just went back through your gallery. Your recent pictures have more vivid expressions, facial characteristics are better placed, and your body lines and positions in particular are growing steadily more dynamic instead of stiff. Your art is not regressing. Presumably your expectations are rising.