Hi J.,
I had some problems with plugged ducts too. My son is now 5 1/2 mo. and I HOPE we're done with the problems. I did all the same things you did without relief. But i did determine that the cause was most likely not drinking enough water. Especially in the heat of the summer, make sure you're drinking at LEAST 1 liter of water daily. Sometimes the plugs could just be pressed out while I nursed, but other times they were very painful and lasted about 24 hours. Here's the things that worked best for me:
1. Right before I nursed him, I took a very hot shower and let the water run on the plugged duct. When I got out of the shower, I put him on the breast ASAP (before I even put on clothes!)
2. I normally nursed in the cross-over position. If the plugged duct wasn't loosening with the hot shower, i positioned the baby's mouth with his chin closest to the plug. This can be a little tricky, as you may be nursing him upside down. I'm pretty sure Kellymom advises this technique to be a myth, but it REALLY REALLY worked for me.
3. The last thing i did was similar to #1, but I'd have the pump handy. When you have a plugged duct, sometimes the baby doesn't want to eat from that side b/c it's too much work or maybe they're just not emptying the breast. So i would (with my husband's help) pump while the hot water is hitting the breast.
And about the blood...all the material i've read says it is no problem for the baby to have a little blood in the milk. Although you wouldn't want to nurse on that side if it's injured. If the plugged ducts and blisters are a weekly occurance, maybe you should make an appointment with a lactation specialist, just to be sure your baby is latching on correctly. The La Leche League is also a GREAT support system.
I hope this helps. Let me know if you have any more questions. Or if these techniques work for you.
K. Fradley