Ouch!

I have been ebf my son for almost 7 months now. The very first week after getting my milk in I had extremely painful, swollen breasts that NOTHING could relieve. One night I was crying in so much pain my mom almost took me to the emergency room. After about a week of excruciating pain, I got through and things seemed to be smooth sailing. My little guy is a great eater, at almost 23lbs. Yesterday my left breast hurt very badly, to the point it reminded me of the first week of pain, but I just kept feeding him as normal and hoped it would work out. I pumped after he was finished eating, as I always do and used heat and warm showers to try to get it to go down. Now almost 48 hours later, it is not any better. There's a large hard lump and a red warm patch where the lump is. It doesnt seem like I have a clogged duct since my milk seems to be flowing fine, but I'm not sure. What could this be? Can mastitis develop this late?