I am 5'3 about 110lbs and I don't know which size to get 350 375 or 400

I am being told different things and ultimately I want to look natural yet curvy I have a nice bubble butt o I want to be well proportioned but not too big or overdone.  I have a small frame and athletic build. I'm currently wear a 32b but there is space in my bras the A cup bras although fit my breast they are too close and don't fit right. I need help I keep jumping from one side to the other cant seem to make a decision