Hi mate,
Since your condom broke, you were at risk. However, not all CSW are HIV positive. She might be negative like you as well. Do not panic as you wait for your test. Please do not google that much, to protect yourself from HIV anxiety, I've been there so, its not fun at all. Keep yourself busy. Cheers mate!
DUO test at 28 days. You had a risk, probably on the low side.
I would not have unprotected sex with your gf.
STD questions post in the STD forum.