it's normal. after birth, also might expand. but also depends on individual n depends on whether you r bf or not.
for me, i use bra extensions (which i bought fr john little marina sq, can find at the counter).
only recently (6 months after delivery) then i buy new bras.
i wear nursing bras whenever i'm home. n padded ones (w/o wires) when i'm out. i get nursing bras fr giant. cheap cheap. the rest at those normal lingerie sections (in JL or taka).