Pretty dang good for only a couple of months worth of expierence.
A few ideas:
First of all (you'll hear it so many times it'll make your nose bleed) draw from life as much as possible. If you can't find someone to let you draw them then find photos. Draw using reference.
Also when drawing anything mechanical use a straight edge. It makes a world of difference.
Study how shadows form shapes on objects. For instance in your drawing you have defined the muscle on this guy using mainly lines. Try defining ,say the abs, using shadows instead of lines. See what happens.
Get yourself some good black and white portrait photograph referance and study how the shadows fall.
Keep at it. Draw as much as possible, you're doing great so far.