wow, good for you man! here's a few things that you can do:
-eat more dead flesh, ie more protein in your diet.
-do push ups with slower tempo
-start doing pullups/chinups/dips if you can. i usually manage to do these whenever i play bball instead of going to the gym.
-buy a pair of dumbells, best investment you can make if you wanna pack in the muscles

all the best man. well, if you wanna start on whey protein supplements, by all means go ahead. just remember the general rule: 1gm of protein for every pound you weigh, but imho you would need to be doing a lot more than just push ups