Don't worry, you're beautiful just the way you are and it is completely normal, you shouldn't hate yourself because of it!
Those who were mean to you about it are obviously messed up in the head, no one should be bullied because of that, it shows they were the kids, completely immature.
You could try the supplements as long as they're not harmful for your overall health, but having small breasts shouldn't be something that you should be worried about every day.
This is coming from someone who has boobs that are visibly different sizes, so trust me I know what it's like to be insecure about something like that.