The first thing I might try is sleeping partially upright, this will help keep your diaphram from being pushed on so much and help you breathe easier. If that doesn't help, I would suggest getting a second opinion. Even if they are panic attacks there are medicines you can take while pregnant to help. Having suffered from them myself, It doesn't have to feel like anything is bothering you for a panic attack to occur. There is usually a trigger but you may not even know what it is.