Sounds like how my cellulitis went as well, it's nasty and needs proper treatment quickly (or, if not that, proper investigation). I ended up at the minor injuries unit at the local A&E with mine as it was very swollen as well and I'm on immunosuppressants.
I was given Co-Amoxiclav on a very high dose and it still flared up again after that. They said they had me on the highest dose they could of the antibiotic equivalent of domestos so were a bit flummoxed!
They suggested keeping my foot raised about my head for at least 48 hours and it did the trick :)
Still took a while to get back to normal but it got shut of the infection along with the antibiotics.