The problem with buying clothes that are a few sizes too big is that they wont fit right or be flattering to you while you are pregnant. If you are already feeling self contious about your weight gain, wait and buy maternity clothes instead of clothes that are too big. There are so many styles that make you look cute pregnant rather than just looking baggy. 15-17 weeks were the hardest for me because I've always had a flat stomach and I was just putting on enough weight to look chubby, not pregnant. So I was super worried about it and kept asking my husband if I looked pregnant, not just chunky. So I started to wear clothes that accentuated my growing belly. Skinny jeans, tops with half sleeves and strechy fabrics made my belly stand out. Also baby-doll style tops helped make my little tummy stand out (and my larger breasts). I also wear long shirts that smooth the line from belly to pants that accentuate where the baby is sitting. I still carry fairly low, so it may be different for others, but it made people start asking "when are you due," rather than wondering if it would be rude to say anything.I would say if you NEED new clothes get ones that fit, but keep in mind that they wont fit for long. But if you can wait, get maternity clothes. That way you don't have to buy two new sets of clothes for your expanding middle. I'm almost 20 weeks and my jeans still fit me everywhere except my middle. But I use a hair elastic or rubberband to hold the button together and get long shirts just incase :). There are lots of things you can buy and wear the whole time you are pregnant, (shirts, dresses etc.) just hold them out from your tummy a foot to make sure you have growing space. You just don't want to get clothes that make you feel worse about yourself.Plus you don't know what your body will do after your baby. I know people who hold onto the extra weight for a long time and then others who have the excess melt off in no time. So if you buy new clothes that are a bit big, and you are one of the lucky few and the pounds drop in no time you are stuck with a bunch of jeans that don't fit. If you hold onto the weight, you may be fortunate enough not to have to buy new clothes because the larger ones fit you now. It's really less of a gamble to wait and see how your body changes before you buy clothes.Hope this helps!