Not straight, not curly, not wavy?

My hair is super heavy. When it’s long, it seems to mostly straighten out but when it’s shorter than shoulder length, it starts to curl. When I was younger, before I got such thick hair, it was always super curly. Do you know of anything that’ll give my hair some of it’s natural wavy curly ish texture back, even though it’s super heavy?

I’ve tried using the catwalk curls rock amplifier, which works well when I’m wet setting my hair but even that doesn’t get them to stay even wavy for more than 6 hours.