Masturbation is natual. But too much masturbation can lead to a damaged penis. I know that if you apply too much pressure on your penis while masturbating, it is possible for you to damage the tissues within the penis. I also know that tissues are made from cells. Cells have the ability to multiply themselves. So maybe if you just give some time for everything to grow and develop back into place, then I'm sure your muscles will be up and running again. I also learned in school that cells need alot of water to survive. So it would be good to drink lots of water and eat as healthy as you can. Don't even mess with your penis, you may damage it more. Try sleeping on your back. Don't wear very tight underwear. Just relax. You might not have the chancce to "get it on" with your girl when she comes back.. but I'm sure if you eat healthy and drink alot of water... you'll will be able to soon. If the problem continues for another month, notify a doctor. I hope the best for you!