is there a way to check imessage history

Your question is a bit general. You can look back through the messages you have on your device. If you're logged into the same Apple ID and using iMessages on other devices, you can look through those. Your cellular bill will have dates, times and phone numbers for any SMS messages.

What, exactly, are you trying to find out?

eddiethisguy wrote:

We both use my iCloud so how could I tell

You would both have to be logged into the same Apple ID. In my opinion, if you know her Apple ID password and use it to spy on her, you are doing something very wrong. I agree with the previous poster. If you can't have an honest conversation with her, it's time to consider whether you're really in the right relationship.

Only if you are logged into the same Apple ID as she is. Or, you could ask her. But, really, if she wanted you to know, she'd probably tell you.

eddiethisguy wrote:

I’m trying to find out if it’s like a different thing altogether like if I logged into it from another device can I go to the same messages like an app or something

Find of if what is a different thing than.....?

iCloud has nothing to do with iMessage. The two are separate services offered by Apple. You create an account in each and sign in to each using an AppleID.

BTW, when you do use the same AppleID for an Apple Service (iCloud, iMessage, FaceTime,...) then you share the exact same account. Everyone using that same AppleID receives and can see everything anyone else with that AppleID sees. There is no privacy nor separation of information at all if sharing an AppleID.

It’s not worth the trouble, if you suspect it then it’s more than likely time to make some important decisions.