Definitely take the antbx, and I would even try to get a second prescritption for them to have them onhand in case it comes back. You do not want the infection to go into your lymph nodes, as it did for me, and you don't want it to become an abcess.
I would suggest though that while you take the antbx you also take 6-7 raw cloves of garlic a day for 7 days. Mash it into a paste with olive oil and salt, eat it on crusty bread, and it will be edible. Also make sure that you are not anemic, up the iron intake in your diet, and REST. No upper body strain for at least the next few weeks-- and this includes slinging your baby. Take Ibuprofin as opposed to other pain killers as you want something anti-inflammatory. Check with your dr or mw to be sure but I think you can take double the dosage recommended on the bottle. Continue to take the Ibuprofin even after you feel better because you don't want the ducts swelling up again. Castor oil packs (with heat) will also help. Do them at least twice a day. Eat raw parsley if you have oversupply.
HTH, PM if you have more ?s or just ask, I am a mastitis "expert" unfortunately.