Boob problem...

I have the exact same issue, my right breast is a c cup meanwhile my left is an a cup. Originally I was really bothered by it but over the years I've gotten over it with the help of family and friends. My mother and grandmother went out and got me silicon bra inserts(you can get them on Amazon for around $20 depending on the size)- which definably boosted my confidence in public. And at home my husband doesn't seem to care- he just tells me to keep an eye on it in case it's cancer related (breast cancer runs in my family).
My best suggestion to you would be to spend the cash on the inserts, best investment since I got my cell phone.

My breasts are relatively the same size (the right one is slightly smaller in overall cup size), but one breast sits higher than the other. My right breast, though slightly smaller, sits higher on my chest wall than my left. I'm a 30D and it drives me crazy. My husband says he barely notices, but I don't know how to believe him when the difference is so glaringly obvious to me. I have gel inserts to place under the right breast. I use them mostly because bras my size are really hard to find and very expensive and the gap between the bottom of my breast and the bottom of the cups causes my bras to dimple after a while and becomes noticeable through my shirts. Removable padding helps too, I can leave the padding in the lower breast and take it out of the higher one when I want a "the girls are on display" look. Corsets are nice too. Mushes the bottom and rounds out the top. You can adjust the girls for a more comfortable look and they are great for back support (can't slouch in one of those suckers lol)

My friend uses the It works body wraps to get her boobs smaller! I use it for my tummy. Since boobs are fat and these target that its a wonderful treatment. Oh just cover your nipples the gel is not allowed on super sensitive skin! Uh here is the website:
https://wannahottiebody.myitworks.com/Home