Please forgive the delay in my reply to you, I was unwell. I am sorry to read of your discomfort and hope I can help guide you here, but please also understand that online, no one can state with certainty what anything is. All I can do is offer my best educated guess based on what you wrote.
It may indeed be discomfort from a bra. However I would not expect that to last so long; when you removed the problematic bra that discomfort should have quickly eased.I asked you if you had chickenpox because I wonder if you could have shingles.
Shingles is a reactivation of the chickenpox virus, and in most people, it does cause a rash and varying degrees of discomfort from tingling to painful agony. The reactivated chickenpox virus inflames a nerve, and the pain of nerve irritation can be described as electrical. Because shingles does travel along a nerve, its felt..most of the time...only on one side of the body in a pattern called dermatonal distribution. The way you describe it under your armpit and breast could be so. However, you do not have a rash and most people with shingles do have a rash of some sort...but that does not mean you can not have a mild case; some people with shingles have no rash at all.
If this was shingles, if caught in the first day or so, antivirals can make it last fewer days and with less pain. That time frame has passed for you, but I can not state for sure that it is or is not shingles. You have had this for many weeks which is a long time to be in discomfort, you also had an swollen lymph gland that says that there is (or was) something going on (which may have been the acute stage of shingles). I think it is a good idea to have your health care provider see and examine this to make sure nothing horrible is happening and to confirm...or deny my guess, and to give you appropriate treatment for whatever it is he or she may find. Here is more information about shingles: http://www.webmd.com/skin-problems-and-treatments/shingles/shingles-topic-overview
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