Please help

Hi I have been breastfeeding my baby boy since he was born which is now 2 months …. I don’t seem to have much supply hence use formula also when required…. However I need help with my sore nipples although my son latches correctly but he still keep hurting me very badly also he has a habit of keeping it in his mouth and latching on it very lightly which I doubt give him any milk and then sleep. Please suggest any thing which helps in fast relief of sore nipples so that I don’t have to compromise on my son Breastfeed… as when it hurts I pump it out but that doesn’t give much output rather it gives more output when he latches himself… not sure why I don’t get much when pump… please suggest