Several people in my family use CPAP (Continuous positive airway pressure) machines to help them breath while they sleep. I don't know much about them though.
There are also anti-anxiety medications that could just help calm your heart (Ativan is what I use, but I would talk to a doctor about it) But I don't know how that would react to what you are already using.

Or if you don't want to add any more medication/machines into your life there is always meditation. Just take slow deep breathes and tighten your solar plexus. Imagine you are on a beach, or at your favorite place in the world. Narrate to yourself a story of a calming situation.
Writing in a journal right before bed can also be helpful.

That's all I can think of right now.