This could be me too ! There is rhyme or reason; people around me have suggestions....coffee, using a phone or ipad (blue light affects the brain sometimes), too much activity too late...etc.etc. Nothing makes a difference. I've been like this in peri for the last year and a half and I'll be honest with you there are days I resort to a tiny amount of lorazepam to help me drop off. I feel exhausted all the time, yawning and cant keep my eyes open, but...the moment I lie down to sleep.....ta da lol
There are two things that sometimes help me, but you have to really focus and commit to them.Relaxation and mind distraction games you can 'play'; You know the type of thing, counting down over and over from 100 to 0 in reverse. Lying on your back and visualising every part of your body being warm and heavy. There is probably an online list of suggestions somewhere. The one thing I will say, which is easier said than done, it to not 'put pressure on yourself' to sleep and feel anxious if you don't drop off. The more you think about not sleeping, the less likely you are to sleep.