Your chances are slim to practically non-existant. From a technical standpoint, there is a greater risk of infection if menstrual blood is present. However, it is very, very encouraging that you tested negative at this point. It is considered a definitive test 13 weeks after your last unprotected encounter. That is because this is the maximum time it has taken for normal seroconversion (turning from negative to positive) to take place. But seroconversion usually happens within six weeks, and thus most people do test positive after six weeks if they are positive.

To be safe, one must think rationally. First, stop having unprotected sex (for the moment). You and your partner must take an hiv test 13 weeks after both of your last unprotected sexual encounters with anyone, including eachother. Until then, use condoms. When you both recieve negative test results 13 weeks after unprotected sex, you are safe to have unprotected sex from an hiv standpoint, so long as you remain monogomous.

I am sure though, given these results you are both fine. If any of this is in any way unclear, i'd be happy to reiterate.