It sounds like a clogged duct, and hopefully you've successfully dealt with it by now and are feeling a lot better! If you are still dealing with it though, here's one more suggestion, a variation on the hot washcloth, which never worked for me - couldn't keep it hot enough long enough to do any good. Instead, fill a big bowl with enough water to lean over a counter and put your entire breast in the bowl, past the hot spot, which sounds like will be pretty deep for you. Massage from behind the spot while you're soaking, soak for 10-15 minutes, then express, refill the bowl with new hot water as needed, and repeat until you feel the plug release. There may be several plugs, as it is crystallized milk. I find it best to do this during nap time or after my son has gone to bed so that I can repeat as needed, as one time it took me 2 hours to get the multiple plugs out. A bath is another great option, as you are more comfortable while doing this. I had over 12 plugged ducts with my son between 2 and 14 months, I still have to be careful of them.
The gravity nursing and chin towards plug nursing is essential. Also, have baby suck from that side only until the plug is cleared. Pump or express to comfort on the other side while doing this.
If you find you get them repeatedly (hopefully not an issue for you!), apparently many women have luck adding a lecithin supplement to their diet. I tried this, but for me, seemed to make matters worse.
Contact a La Leche League leader or group if you have more questions either about this or other breastfeeding questions. They have great information and support. www.llli.org. Look under resources, then find a leader/group.
Good luck! Feel free to email me for support. You're doing great for your baby.