I struggle with insomnia and use meds to help, but struggle to sleep well, even with the help of meds.

So I have started to do 20min of 4-7-8 breathing before I go to sleep and I struggle! I struggle to slowly breath out for 8 seconds. And then it feels like O2 deprivation and I am gasping for air when I am allowed to breath. I am wondering if this doesn't add more stress to my body in an attempt to calm it. Maybe there is some other technique I can try to activate my parasympathetic response to relax before bedtime? Or should I just shoulder through this unease until it becomes easy?

I have been doing this for 2 nights now and experienced an slight improvement in how fast I can then get to sleep and sleep quality.

Any comments are welcome!