If you're following the syllabus, you should never have OG problems before we try them in class - the OG problems are always listed on the syllabus AFTER we've done that relevant lesson in class. You may want to bring your syllabus to class to discuss with your teacher if you are confused about the sequence of anything. You can also call the office (800.576.GMAT) for more help with that.
Oh, I see - now I'm reading your second paragraph and you're saying that you're choosing to do some of these problems in advance yourself. That's a bad idea - don't do it. :) It's better to learn the material first and then use the OG problems to test your skills and understanding.
Don't feel that you have to do all of the OG problems every week - in fact, you should NOT do them all. Save some for later in the course and after the course ends. You're going to want to start reviewing at some point, and you're going to want to be able to do random sets of questions (because they also come at you randomly on the real test) - but that will come later in the course or after it's over.
Also, there are around 1,500 problems total in all 3 of the OG books. You do NOT need to do all of them in order to prep for the test. You're going to do a lot, but it isn't actually necessary to do every last problem. So don't let that totally overwhelm you. It's a quality-of-study game, not a quantity-of-study game. :) For what you do study, you want to study carefully and thoroughly.
You may be interested in these articles:
http://www.manhattangmat.com/articles/a ... roblem.cfmhttp://www.manhattangmat.com/articles/GMATprep-SC.cfmhttp://www.manhattangmat.com/articles/CR-assumption.cfmhttp://www.manhattangmat.com/articles/a ... estion.cfmhttp://www.manhattangmat.com/articles/a ... roblem.cfmhttp://www.manhattangmat.com/articles/a ... roblem.cfmThey talk about how to analyze problems - you can see that the analysis is pretty extensive, and this is why I say you don't need to do all of the problems. It would take forever to do that kind of analysis with 1,500 problems! Let me know if you have any questions about the above.