Formula/breast milk

Hi everyone

Pls help me out,, am a first time mom, I breast fed my baby for a month without anything added so I started giving him formula and breast milk together

I give him formula in the morning and breast feed him in the afternoon

I’ve been doing that for some time now

The problem now is that my breast has sore it’s really painful anytime I want to breastfeed him,sometimes I will start to cry cause it’s very painful

I don’t know what to do

Should I stop the breastfeeding for now or still continue

Pls help me out