You need to be comfortable, so I don't see a problem in spending some money on a few key pieces for your wardrobe. I am in the same dilemma as I am going to be more pregnant over the hotter months than I was last pregnancy, so none of the clothes I have already are suitable and like you are more suited for an office than casual. I want to comfortable and not be afraid to walk out the front door, so I have decided to spend on a few pieces.