I Reckon it is Suppose - A way to say 'I guess' that sounds like you're from the 1800

A way to say 'I guess' that sounds like you're from the 1800s and you're also mad about something.

I Reckon it is Suppose I'll finally stop eating cereal for dinner.

I Reckon it is Suppose I'll actually take a shower.

I Reckon it is Suppose I'll stop arguing with my little brother.