Remember you need to give your muscles a chance to rest. This is where the building takes place and that rest period is also to make sure you don't injure yourself. You should also decide what your goal is? Do you want to build, tone, burn fat etc. I've never heard of taking a week off to break a plateau, that's not to say its bad, but here's a little piece of advice. I'm no expert but I've learned that you want to at least rest your muscles for 24hours. So if you work chest on Monday you should not be working chest on Tuesday. Rule of thumb never work the same muscle group 2 days in a row. That has been reiterated to me from pretty much every personal trainer that I've spoken too.
From what you said about your routine it doesn't seem like your giving your muscles a chance to rest. If you lift for 3 days and then do cardio/volleyball practice for 2 days then on the 6th day you can rest and perhaps do a light cardio workout on the 7th day. If you think your volleyball practice isn't really that taxing you could probably working with weights again on the fifth day. Also try changing up your routine or adding a supplement to your diet these are some of the things that will help you break that plateau.
Changing your routine would be like instead of chest and triceps, you do chest and back or perhaps try some new chest exercises or even switch up the order of the exercises that you do. Your body becomes accostomed to a routine after about 8 weeks or so, so try and keep changing it up so that your body doesn't become used to the same thing over and over.
Protein is, as you will read on this board, a great supplement to add to your diet. However, you should take a look at your present diet and see if there is any fine tuning you can do. Cutting out fast food, eating more complex carbs or even changing your eating schedule can also work wonders in breaking that plateau.
Hope this helps and I'm sure some of the more experienced folks here will chime in with even more good points.
