Look up a book called solitary fitness by Charles Bronson (not the acttor) this book was writen by a prisoner who through using nothing more than a chair and his own body was able to go from doing only a couple of pushups to over 1,000 a day.
You probably don't need to buy his book, but at least look up his program. Also try things like dips to increase tricep strength.
Well, four is better than three! Just keep doing them every day and it will come. Don't give up! Weight training is great too!
Good luck!
Always work to muscle failure and no further. IN other words when you feel like you are going to die, do one more and then stop.
If you can, work with a trainer.