blocked duct or mastitis help

So my babies 5 months old EBF in this UK heatwave shes been feeding less and shes also at that distracting age where she pops of to look at everything last night i woke to my right breast kinda aching and its been getting worse throughout the day Its sore to touch in a certain space i pumped it till it was empty today and have been putting baby on that side as much as possible but im not sure if im developing a little red patch now im worried has anyone got any tips or advice for me i found a hot shower on that breast to be quite painful i also have a headache not sure if its sun related or boob pain related? thankyou