I am 18, 5'4 and around 155 pounds.
Currently my boob size is a C for my right and a D for my left.
They are very uncomfortable, and so uneven. If I lose around 30 pounds to reach my target weight will they shrink a size down or anything? Also is it healthy to lose around 3 pounds per week?

For many women, a decrease in breast size goes along with some weight loss simply due to the composition of breasts.

You may see a fair amount of weight loss in the first week or two, but it will likely taper off and the recommendation is a couple of pounds a week. This is easily achievable with sensible changes in eating and exercise habits.

Think healthy lifestyle changes for long term health and weight loss benefits instead of a "diet" which often is short term (and potentially dangerous) if too drastic.

I would say, if your looking to lose weight, try and keep it a bit less boob size loss, and a bit more on the stomach, inner thighs, and arms. I find a C cup just as attractive as a D to be honest. Oh and 3 pounds is good. Any more than that and you'll have a weight rebound. And getting back to boobs, mens favorite topic it seems like probably, I know, try and "tone your boobs" if you will. As hilarious and stupid as it sounds, I don't mean muscles popping out of your boobs, but you should work on your shoulders, upper chest (above 'em) and ribcage. That gives them more support, along with your hips, and makes them sag a LOT less, so they're a C, but look larger, Also, APPARENTLY their more comfortable, and are in all honesty a lot more attractive to have large breasts that retain their shape while shaking to go into maximum detail... Also, try to gain muscle (the non visible ones to be sexy) with losing weight or they'll just feel the same or heavier than before. Wow this is way too long, but also, with exercise, they should even out in size, because the extra fat with weight is just disproportionate between the two, so you'll probably lose that with the easier exercise, and then as you move up they'll eventually get about even. But tbh, men just stare at the crack between them :O... not the actual breast in itself. Be proud of your body though ^_^ men love it in a slightly pervy way and in a we like confident women way.