I've found both times normal trousers seemed to get tight around my middle pretty quickly but normal tops and dresses were fine for longer.
I'm wearing maternity jeans now at 9 weeks. They have elastic panels with the bit of elastic and a button, like kids trousers have, so I have them on the tightest one just now, but they're still better and more stretchy than normal jeans. My maternity leggings and over bump stuff is still too big just now.
Last time I was huge but was still in some normal stuff the week I gave birth! I'd bought normal stuff made from stretchy fabric a size up, like vests and tops, which did me through the whole pregnancy.