Ditto to what Paxiled said. It's not like an aspirin or a sedative, where it can be taken "as needed'. It would take weeks for the increased dose to make ANY kind of difference. Please talk with your doctor if you're having an increase in symptoms.
How long have you been on the Prozac? That's a fairly low dose, it may be that you need a higher dose. I was on it during my pregnancies, and I required a higher dose of the Prozac than I did comparitively of the Zoloft and Lexapro in order to have the same level of effectiveness.
It doesn't work that way -- upping your dose will take as long to work for you as starting did. Also, Prozac is a more stimulating antidepressant than some others, so it just might make you more anxious, though it might make you less to permanently up your dose -- in other words, no guarantee it will do what you want, it's trial and error here.