I've been having sex with my girlfriend and recently my penis has been more itchy than usual and ive noticed small white spots appearing on the head.?

Yeast infection? Your symptoms suggest yeast infection, especially if uncircumcised and the "white spots" are under the foreskin. Vaginal itching or discharge also would fit with yeast. STDs are possible if your relationship is new and/or either of you has had other partners in the past few months. If so, both should see a doctor or clinic. If not, you could both try an OTC yeast cream, but see doc if no response.