Try reading the fucking sticky over at
>>>/fit/Doing the starting strength program by Rippetoe, eating more meat and drinking milk will make you feel so much better. Add fruits and veggies and you'll improve even more.
Get vitamin D, fishoil and ZMA. Protein powder (make your own gainer) if you struggle to eat.
Fuck taking drugs, exercise should be prescribed by doctors, both in psychiatry and in general.
Just doing pushups in the beginning is enough. Do them until you can't do any more (until "failure"). Rest three minutes, then start another. Do five sets of pushups that way. Do this three times a week max, but preferably at least twice.