What to do if I have been on amoxicillin for 2 days and might perform oral sex on my girlfriend, will she possibly get strep or get any other infections from it?

Depends on your... Depends on your infection and it's location. I'm assuming it is your throat. Why not wait until it clears? You can express concern for her and that will help your relationship, although i think the risk of transmission of a major "bug" is not likely!