Alexii,
I, too, wear a 38B, and I wear one most of the time. Like Hammer said, it finally comes down to personal choice. I choose to wear a bra because it keeps me from jiggling, it keeps my nipples from showing through some of my shirts, and I like how I feel and look with one on. So, if wearing a bra feels good to you and feels like the right thing to do, then by all means wear one.