bra size?

i usually wear 32A, but after having kids, i stop wearing bras. after my 2nd child, im starting to wear them again, and find that the cups of 32A still fits me perfectly, however, the straps are sooo damn tight! making me feel so uncomfortable. im confused to if thats how its supposed to be and because i havent wore bra in a long time im not used to it? or im supposed to go up a size, but stick to A cup? if thats so, i just wasted so much of my hubbys money buying a lot of bras for me, like 6pairs :'( sighhh...