Hey dude, you need to get rid of all the bad health habits and start living a healthy lifestyle. I don't say this lightly, your overall health is shown on the hardness of your penis.
Start by cutting the fat, quitting smoking, eating healthy foods and exercising more regularly. If you are on any kind of medicine, then check to see if it is bad for erectile strength and request a change.
Lastly, you can try taking herbal supplements to improve blood flow and strengthen your erections.
If you want to know more, pm me for a free ebook on ED or simply check out my profile