what does these words (I heard them in a song) mean? DEEP IN THE HEART OF ME?

Answer 1

It's a figurative phrase, meaning that whatever it is, or whoever it is, has really affected the speaker on a deep level. i.e. When my boyfriend left, I was hurt "deep in the heart of me".

Answer 2

Here's the song. It's called 'I've got you under my skin'. He's saying that he loves her so much he can't resist her. The allegory of the heart is often used in 'love' so to have her deep in his heart means he really loves her.

I’ve got you under my skin
I’ve got you deep in the heart of me
So deep in my heart that you’re really a part of me
I’ve got you under my skin
I’ve tried so not to give in
I said to myself this affair never will go so well
But why should I try to resist, when baby I know so well
That I’ve got you under my skin
I’d sacrifice anything come what might
For the sake of having you near
In spite of a warning voice that comes in the night
And repeats, repeats in my ear
Don’t you know, little fool, you never can win?
Use your mentality, wake up to reality
But each time I do, just the thought of you
Makes me stop before I begin
‘Cause I’ve got you under my skin
I’d sacrifice anything come what might
For the sake of having you near
In spite of a warning voice that comes in the night
And repeats - how it yells! - in my ear
Don’t you know, little fool, you never can win?
Why not use your mentality, wake up to reality?
But each time I do, just the thought of you
Makes me stop before I begin
‘Cause I’ve got you under my skin
Yes I’ve got you under my skin