This blister has been showing up on the same spot (below my left breast) 5 times now within a span of 2 years?

That type of skin lesion is called intertrigo. Its a complicated situation that starts with irritated skin where it rubs against other skin, then the combination of moisture and irritation make the skin susceptible to invasion by yeast and bacteria. When blisters are present without a lot of surrounding redness and burning, its likely to be caused by a Staphylococcus aureus infection, although yeast may still be part of the problem. A combination of antibiotic and antifungal creams is often helpful, but make sure its a cream and not an ointment. There's treatment advice at the link. For the long term, find a breathable bra that provides enough support to prevent skin to skin contact. sheer sports bras might be the best choice. Padded bras can cause problems by trapping moisture. Whatever you do do not any substance that has the potential to cause more irritation.

This problem can be solved easily,

what you need is patience.

Just do this,

Take 1 glass of warm water add 1 lemon juice to it.

Drink this lemon water in the morning at 8 a.m.

for 48 days.

Apply coconut oil on the blister spot.

even though your problem will be solved with in 15 days,

you have to continue til 48 days.

that's all you need to do. God Bless.!

Change your bra

Throw all brads away and get new ones.............

I'm constantly changing my bras and washing them as well

So change your bra.