ask for my rate to be higher? How bad would it look for me to go back into work tomorrow, and ask if there is anyway that the rate is adjustable, even though I just signed a renewal for 6 months today.

I didn't have much of a chance to talk about the details of it with my boss prior to signing it. However, he had asked me over a month ago, and periodically inbetween, what my intentions were, meaning, whether I was intending to stay with the company for now or look to move on.
Today he printed it out and asked me to come over to his desk and sign, and then afterwards, sat down with me in the boardroom to discuss a different opportunity that may be coming up in the company.

I'd hate to look like a fool for asking for more money after I signed the agreement yesterday, however, I never sat down with him to talk about the rate before I signed the renewal.