Weird breathing that makes me anxious before sleep

Mine is 5mg 3x a day, making it 15mg total. I'm already anxious about the third dose. It not only make me so weak and shaky I thought I was going to pass out, but it makes my chest feel heavy and my breathing feel slow. It scares me so bad I often jolt awake before finally falling asleep. Should I skip the third dose completely? Can I take a diphenhydramine gel or 15mg melatonin? If I choose diphenhydramine, can I do it like four or five hours after the third dose? It's only been a week of this and I'm already scared and wanting to get off.