Sympathies from me too, Smac, mastitis is just horrible.
IMVHO, Amoxicillin is a slightly odd choice for mastitis - it's usually Flucloxacillin with or without Penicillin (Fluclox covers the most commonly occurring skin bug - staphyloccus - which is usually resistant to Amoxil). So if you don't feel better within yourself in 24-48 hrs max. I would ask for an urgent review.
Keep taking your Ibuprofen +/- Paracetamol for pain/shivers/general crapness.
I found hotpacks before a feed, followed by coldpacks after the feed helpful (but made the sweating and shivering worse...)
I offered boob everytime I passed my baby. Every time. Well into double-figures-per-day times.
Yes, do pump for relief. If it gives you relief - I always found the baby more effective than my fancy-pancy pump - pump made the 'healthy' part of my breast softer so relieved discomfort indirectly, but never cleared the blocked duct/gland. Ever.
Lots and lots of massaging. I had to beg one of the BF support nurses at hospital to do it for me because I was too sore and couldn't hurt myself more IYKWIM. Apparently the policy is for them to be 'hands off', but my tears begging softened her heart and she did it. I went home (this was 2 years ago with DS3), he had a feed - problem solved.
HTH a bit. I'll come back with more if I remember anything.
Sorry, must run, squealing from the bath - and that's just DH... 