Is my girlfriend pregnant?

okay so we had sex april 21, 2011 with a condom, we have always had sex with condoms. then the next day we went swimming and then into the jacuzzi, after that we took a shower together. I was wondering if she could of gotten pregnant in the shower? my penis didnt go inside her but maybe the pre-ejaculant contacted her inner thigh region. please help. I am flipping the **** out. also she has weird periods, sometimes her being late and sometimes her being early. I try to bring it up to her but she just gets mad at me and tells her not to stress her out. from what i know she doesnt have any symptoms. No darkened nipples, no lower back pain, no nausea or throwing up. I just dont know when she will get her period, please help