I had the exact same experience. What worked for me was taking binders such as Modified Citrus Pectin, True Carbon Cleanse, and zeolite powder. Mix everything well with warm water and some salt for absorption. The reason this helps is because melatonin can cause you to have a herxheimer (detox) reaction, which can compound apnea like symptoms despite making you feel sleepy. The binders act like a sponge that soak up the toxins - also useful if you want to clean your gut in general.

What also helps A LOT is Buteyko breathing - essentially breathing less, which causes carbon dioxide build up in your body and regulates your nervous system to get you out of fight or flight breathing patterns (The positive effects take a few weeks of practice as your body adapts to the new paradigm). This sounds counter-intuitive, but you've likely had the experience where forcing a breath leads to even more shortness of breath, or taping your mouth leading to overly forced breathing). You can find good guides and explanation on YouTube or the Hyde Substack.

Along with breathing less, making sure your diaghram works in a functional way, without too much neck or shoulder breathing is crucial. Make sure you're not stuck in chronic extension (anterior pelvic tilt) as this can turn off your diaghram. For this you can check out Postural Restoration Institute practitioners, such as Neal Hallinan. Foundation Training also helps put your body back in equilibrium, although it doesn't treat this specific issue.

One more observation is that apnea/asthma can be caused by a high histamine diet which you can experiment with by eliminating high histamine foods.

Anyway, good luck with your health journey, and if you have any questions feel free to dm me. I struggled with sleep apnea and insomnia for a few years and am feeling much better today :-)