My gf went down on me (male) and we think she might have strep throatcould i have caught something from that?

Strep throat itself would be unlikely to cause any problem. However, there are viral infections that can cause sore throat much like strep, which can be transmitted to the urethra by oral sex, especially certain types of adenovirus. For the next 3-5 days, be alert to possible painful urination and/or discharge from the penis and get care ASAP if anything shows up. If no symptoms, all is well.