~PP~
Go to the doc. and get a prescription for viagra. If your erection isn't as big and as thick as you think it could be, I think Viagra will help.
Someone mentioned jelqing...I don't know the specifics but I think it goes something like this...masturbate but don't orgasm, do this frequently and repeatedly, and your penis will grow in length and girth. Someone can explain this better I'm sure. It's common practice in some cultures.