The story is progressing, and that's important when writing a long story. Each scene has ended at a place that leaves your reader wanting more. I don't need to tell you how important that is.

You have used this scene to get Ashley and Ethan back into their relationship, and I'm sure that's important to the rest of the story. Your reader needs to know and care about your characters. You're doing very well with introducing the characters.

Minor fixes:
Taking it as a sign that he could go further, he started caressing her butt on the cotton skirt she was wearing before Ashley withdrew her tongue and slowly moved her head back, away from his.
Your reader knows that if Ethan was caressing her butt through her skirt, then Ashley was wearing it. You can make these sentences more succinct like this:
Taking it as a sign that he could go further, Ethan began caressing Ashley's butt, feeling its softness through the thin cotton of her skirt. Use active voice.

Ethan opened his eyes, his hand was still moving along her ass while his fingers were in her hair. His fingers would need to be very long if his hand is on her butt and his fingers are in her hair.
Try this: Ethan opened his eyes. His right hand continued to knead her butt, while the fingers of his other hand combed through her hair.

Ashley's eyes narrowed as she stared at him for a couple of seconds, then her eyes started widening, and her mouth opened. "Oh, Ethan it's you! You've changed over the years."
Okay, lets use some active voice to fix this sentence.
Ashley opened her eyes and stared at Ethan for a couple of seconds, and then her eyes brightened with recognition. "Oh, Ethan, it's you! You've changed over the years."

Ethan watched at how her eyes nearly popped out of her sockets when she stared at the bulge in his boxers.

I'm looking forward to reading more of this story.

Bikerider