Hi Amat,
Welcome to the ATT board man.

In seeking to build strength, bodyweight exercises are one of the finest tools that you can employ....
Check out this thread, with some great suggestions from Salty amongst others.
http://www.saddoboxing.com/boxingfor...xcercises.html

Squatting may be an excellent methos of improving overall strength.
It will certainly aid your explosive power and perhaps by solidifying the calves with raises/seated raises you can maximise the strength of your legs.

Also, take a glance at they description of whey protein in this thread;
http://www.saddoboxing.com/boxingfor...ictionary.html

Good Luck.