*Notes: I enjoyed this story. I love it when there is a twist. Your ending twist was priceless. I have included a line-by-line review below.
Red - changes needed (some of the spelling may be different if you are not in the USA)
Blue - suggested changes and comments

***When you least expect them, paranormal events can happen. Take what happened to me. I went to sleep one night and started crossing into other dimensions. There I discovered many Earths travelling (spelling) in parallel, but along different timelines. When the reality of our dimension crosses over the peripheries of another unknown, invisible macrocosm; it is both confusing, frightening, and strange.
***The ever-wandering fringes of different dimensions create junctures in time, where without realising, (spelling) a person can cross over. When there, you learn some things remain the same, but others change dramatically. And now, I know, once you begin your travels, you can't return!
***I'm Dave Grant, a marine engineer. (should Marine engineer be capitalized?) This is my story.
***Saturday the 1st of May 2022. I awoke with a start and looked at the bedside clock. It was early, so I turned over, then realised (spelling) Elanor, my partner, wasn't there. I called her name but received no answer.
***I never expected the answer I got, "Have you been drinking again? You can be so cruel when you want to be. You know she died when you drunkenly crashed the car, with her in it," (period not a comma) Then she cut me off.
***"Yes, a week in advance," (period not a comma) She gave me an appreciative smile and before leaving, said, "By the way, I fed your cat."
***Sunday the 2nd of May. A kiss planted on my face woke me. Looking up, I stared into Elanor's blue eyes, (period not a comma) "Morning, the love of my life."
***Realising (spelling) I wasn't home, but again, somewhere new. I thought fast, and answered, ***It was becoming obvious that I was travelling (spelling) through alternative realities. It seemed when I entered a new spatial dimension, the Dave in that dimension couldn't also be there.
***"Not knowing what to say, I raised my wine glass, grinned (comma) and joked, (opening quote marks) Well, here's to the new me."
***Elanor giggled, and raised her glass, "Long may the new you last."
***... I stared into a red-eyed, mud-smeared face, taking a moment to realise (spelling) it was an army sergeant who saved me.
***Looking down at my threadbare uniform, I realised (spelling) I was wearing a lieutenant's insignia. Somehow, in this dimension, they were still fighting the First World War.
***Please remember, before going to sleep, kiss and hug your partner, and tell them you love them, (no comma) because after you fall asleep, you never know where you will wake up!

FORUM

Ultimate Trinket Adventure [Mainland]  (E) Collect treasures, complete tasks, and win the golden Apple.. #2267246 by GERVIC