capitalization errors in this sentence, My father and I have already visited several states this month.

I'm not sure how many errors you are looking for but, this is what I got:

My Father and I, have already several states this month.

I really only see one error. Father should be capitalized because Father is a title of a person. I would also say the "I" should always be capitalized but, it looks like you already got that. Everything else seems ok.