I think you shouldn't eat any medicine that make you stronger. It's very dangerous. And I think you should ask a doctor, this may be better.
If you want to be stronger, the most important thing is, you have to eat healthily, and also, you should do exercise regularly. You may choose some exercise which can make you stronger.
If you have a healthy diet, and have keep doing exercise, I am sure, you can be as strong as him within half a year.