if you are always carrying Liebs on the right side, your muscles will be used to it - so more likely to be injured on the other side hun

apply heat for 20 mins (wheat pack or something) then leave it for a while, and do it again (i tend to do 20 on 20 off for a couple of hours)

there is a slim possibility of mastitis as well - my mum was never successful in BF either my brother or myself, so didn't even contemplate mastitis - she got it when i was 12!