I've had blocked ducts over the years, to the point of shivering with a temp, but managed to feed/massage my way out of it. But then recently I got hit with full blown mastitis.. VERY different in my experience. This hit really really quickly. only a few hours from 'hmm... my boob feels sore' to shaking so hard with a temperature and vomiting. OMG I've never felt so sick in my life. I couldn't feed my way out of this one... she was so fussy on it (looking back I realise she couldn't get anything out!) I saw the dr and got antibiotics, jumped in the shower and hand expressed. Took ages to get anything at all out.. then finally I got all the gunk/pus out. Was so gross I nearly freaked out LOL. BUt I finally got milk flowing again and DD fed properly after that and it cleared up really quickly.

So yeah, there probably is varying degrees of it. What you're describing sounds to me like blocked ducts and you're managing to clear them before any inflammation/infection sets in.
I agree with this. I've always had an oversupply so have been prone to blocked ducts when ds missed a feed. But a few months ago I got mastitis and I can tell you now, that's a whole different kettle of fish.

Fever, rigors (shivering etc), feeling faint, vomiting, tired, too unwell to do anything, aches all over. I got these symptoms shortly after a blocked duct. By the next day had redness all around the area that was tender and swollen.

I was on antibiotics, and hand expressed and massaged. DS didn't want to feed off the affected side. I had to express until all the pus came out. Then I felt better after 24hrs.