if i uninstall the mod my skin shows up as Steve's when i,am online instead of my skin

if you uninstalled the mod, and the skin didn't show up normally, you should check your internet connection.

Edit: also, try re-apply your skin through minecraft.net.

My skin shows in other versions

which version of Minecraft are you on? did you try without any mods?

Iam on 1.12.2 and the skin dosen't show in vanilla 1.12.2

does other players' skin show up when you are on a server?
you might have reached the limit of a client can query about a user profile for information like skins.
try again few hours later to see if this problem persists.

It been like this for a while now

hmm, have you tried re-install Minecraft? deleting/moving all files in .minecraft folder and let the launcher download them again.

It worked

nice to hear that