Everyone is a little different. What's overtraining for me may be undertraining for you or the next guy.
The best way to be sure (if your very paranoid

) is to keep carefull logs. Log your reps at each weight, # of sets, duration of each lift (tempo) and very importantly your rest between sets. Your rest period can be a great indicator because you may be able to keep the weight but you may need more and more time to recoup between sets.
All this is a little tedious but it's the only way to get quanitative data on your progress or lack of. The proof will be in the proverbial pudding. (did somebody say pudding, yum) give it 3-4 weeks, If you see that you stop making gains or slow down you will need to adjust your routine accordingly.
Its a good thing to log your food intake side by side with your workout, that way its easy to see the correlation....could be that you need to adjust your food intake.