ANSWER: Do some reading on Charles Atlas and the benefits of dynamic tension. It will make you stronger than lifting weights can and costs no money for equipment. A high protein diet is beneficial, but maintaining a balanced diet with a greater intake of water will probably add some bulk faster. Protein is good for muscle building but grains, breads, pastas and an average of 1000-1500 extra calories a day will help. If you want to add mass and not stamina, dont run or do aerobics as this will just keep you slim. If you want to be successful at this endeavor. Tell yourself that you like yourself just the way you are now and anything in addition will just be an improvement. You might have to face that you are the size that you are going to be for the rest of your life and no amount of weight lifting can change that. I went to the gym for 6 days a week, 2 hours a day for 5 years and gained no weight. I got stronger and better defined but no mass change. It had to do with my metabolism.