Weirdly, I struggle more sitting up nowadays, even though for almost my entire life it has been worse when lying down. Ever since starting Evrysdi back in September 2020, I struggle coughing up my own phlegm without help, sometimes to the point where it’s dangerous. But, at the same time, if I lay down and roll to my left side, a cough almost naturally occurs without any effort to bring out, and I have not had a real coughing fit in bed while illness-free ever since. I almost instinctively want to get in bed now if I’m struggling getting this annoying cough out!
I’m sorry you are dealing with that, I know it’s miserable. I would just suggest doing an extra breathing treatment or doing deep breath exercises before lying down, or trying to find another sleeping position while laying down. I have noticed greatly increased phlegm when I roll too far on my right side. You might want to also raise the head of the bed if possible. Have you considered taking some guaifenesin right before bedtime?