sex on period / pregnancy risk??

I love how Glow shows me my % risk for pregnancy, however my SO and I usually have sex while I'm on my period as well. I would like to know the likelihood of getting pregnant on my period. Can anyone help/give me an idea of the risk?😊
here's some info that may be useful⬇️⬇️
We are not ttc. Fertile window begins 5-7 days after end of period. When I'm high risk for pregnancy we use condoms, when I'm low risk we use withdrawal. Never had a pregnancy scare with this method.