Itching in your vulva area can be the result of an infection or irritation. Your boyfriend should not be responsible for buying you a cream. This is something you need to take care of yourself. Get to know your body and how to take care of it.
I'm wondering if your lip has always been bigger than the other. If not, then it's possible you have an infection of the mucus gland or an abscess. If it's painful, see a gynecologist immediately, as this can be a serious condition if untreated.
However, it's much more probable that one of your lips is simply larger than the other. There’s nothing wrong with you. You’re fine. Realize that everyone is different. Vulvas are like noses: Everyone has a nose, and they’re fairly similar; however, there are small variations. Some noses are pert and tiny, while others are more imposing. But they’re all noses, just the same.
The lips of your vulva and unique to you. Some women have small lips, others are larger, and others larger still. And one side is usually different than the other. Dr. J