Eye strain and headaches

I first took lsd this may and since then I’ve done it 4 times, safe to say it’s the best thing ever made, but the last 3 trips towards the 8 hour mark my head starts to hurt quite a bit and when I shut my eyes it has a weird painful sensation I can’t really describe. Sort of like my eyes are stinging really badly only when I shut them. I usually take lsd outside all day and not indoors. I feel this would have an answer to it