There is something I have been meaning to tell you.
"There is something"＝「何かがある」
"that I have to tell you"＝「あなたに言わなければいけないことが」
または、
"...I have been meaning to tell you"＝「あなたに言おうと思っていたことが」
Sentence in context:
"OK, so there is something that I have to tell you. Do you have a minute?"
アメリカ合衆国 
