I'm pretty sure what you are describing is anxiety. Does it get worse when you think about certain things? I've had bad anxiety for the past couple years after I had a bout of depression, the best way to get over the feeling is to think whatever makes you most anxious and sort through it clearly. For example if your worries are over money, write down a budget. If your worries are over labor, do some research and figure out what makes you most anxious about it and see what you can do to relieve that worry. Its perfectly normal to experience anxiety, just try not to let it get the best of you!
Lol I kinda get that feeling too but I guess its just something us pregnant women go through lol