nice pics - you're on the right track! Just a few things: try keeping a lighter hand you seem to have some dark lines which can make the drawing harder to manipulate its errors. Try checking your proportions a little more (they're good but can be better). Also like the above comment, check your negative shapes - this will help make everything more accurate. Great job thus far! I'd love to see more.
Dizon, my instructor is a local artist (Southern California) named Cynthia Grilli. She is very concerned with teaching us to build a quick and solid foundation with an envelope and block in so that we can then take the drawing to a more complete level without concerning ourselves as much with proportion and gesture down the line. Thanks for the tip on the negative shapes - I do need to watch those more closely!
Oruhito - Yes, I must draw lighter. I think I continue to go over the same lines too much. Thanks for the other tips too. I must remind myself to step back from the easel and check my work just as much as I am actually drawing.