Blood pressure tends to drop in pregnancy. As long as you don't feel dizzy or overly tired, then it is not a problem. I'm carrying kind of high and find it hard to breathe at times. I'm seven months pregnant. This is a very, very common complaint.
Most women notice it when they are trying to sleep.
Sleeping in a semi-sitting position, either propped up on many pillows or moving out to the lazyboy, is the best way to ease your breathing. Try to eat only small amounts of food at a time, so an overly full stomach doesn't add to the problem. Other than the huge social and economic situations, there is a physical toll on the body as well. Young teens who haven't completed their own development are more likely to have pregnancy-related complications. Ideally, teens don't become mothers.