4 Years Post Treatment - Discomfort with Retainers

I finished Invisalign almost 4 years ago, and have been consistently wearing my retainers every night since. I have never forgotten.

Recently they have been really bothering me - so much so that I have to take them out in the middle of the night as I can't sleep. When my top and lower teeth connect it feels so uncomfortable (almost tight, but not quite - it's really hard to explain) and I just can't stand it. It's sort of like I'm clenching, but I'm not. I try for a few hours to sleep, but keep waking up at the discomfort, and eventually just have to take them out.

Has anyone else experienced this and got any suggestions for what might help?

Also, this far after treatment, does anyone know if I can get away with wearing them for less time than overnight? I feel like I'd almost prefer wearing them in the day for a few hours.