I started getting horrendously out of breath around 18-20 weeks or so, the tiniest bit of physical exertion would just make me feel like I was wheezing! Even having long conversations I would have to take a break in mid sentence to inhale deeply. I called my ob-gyn when it started and the nurse said that this symptom normally is more of a third-trimester thing and to call my regular doc, so I did. I got checked up and my pulse-ox was fine and everything and the regular doc just said to chock it up to pregnancy. It really frustrated me because it really limited the amount of physical work I could do at any given time. I've had it for two months now and it hasn't gotten much better, but at least I know it's not hurting the baby. I do wish I had gotten a more satisfactory answer then a "just one of those things" kind of an answer though. Sorry you are experiencing it, it really sucks!