Phoneless Chords

I play guitar. Not very well or professionally or anything. I just like to play when I feel like it. I like figuring out chords and hearing how they interact.....man. Sometimes, I sing along with the guitar playing. This can be quite fun, but one answer sort of eludes me. Am I in tune?

I decided to get my recorder that I use for comedy and impromptu interviews on the train and such and record me singing while playing guitar. The result? Decently in tune. Except for random notes here and there. Like, I'll be in tune with no issues and then out of nowhere, some atonal specter of doom makes me sing sort of in tune with the chord but not with the melody, usually at the end of a lyrical phrase. It works, but it's just completely unexpected and makes the song sound like a mistake. And I hear this and think, "I could go for a Coke."