[this is after reading only the first chapter]
Ok. So your premise is a wounded soldier living his life suddenly is reborn into an infant, retains all his memories and stuff. It's a neat idea.
This is a decent hook: "It has been three months since the fighting ceased, yet it all still feels like a nightmare." It comes in the middle of the chapter, and everything that came before it is expository. You spend a lot of time building the history of the war without actually saying anything specific.
You want your reader to be asking tons of questions about this: when was this war? Who was fighting? Why did it happen? What was the result? Who is this guy? None of these questions are in my head.
You would do better to drip-feed those details later on, after you've established the relationships and tensions. I'll give you an example: "a pile of charcoal in the field."
[How did it get there?]
"It's early spring."
[Is that a clue?]
"None of them are burnt."
[Strange. If someone had a BBQ, they would have been burnt. So what gives?]
"Before he died, Bobby and I made a snowman last winter and used the charcoal to make his face."
[That explains the charcoal, but what happened to Bobby?]
Everything in the first half reads like a narrator's conclusion about the evils of war.
Then, you get to the cashier. MC acts offended after telling her to ask whatever is on her mind, then says he's not offended while being noticeably offended. Sensory details would be great in this section to really draw your readers into the moment. What color is the gum packages? Sounds? Smells? Use five senses.
FWIW Every wounded veteran I've ever spoken to has been pretty friendly about sharing what happened to them, from picking up a grenade as it went off, etc.
Also, your war feels generic. I don't know if that's what you're going for, but there's no worldbuilding in this.
Then he gets mystery sucked into some aetheriel world and gets born. This whole section feels rushed, like you were trying to hurry up and get through it.