"That's fine" I thought, There should be a comma after fine.
When we first met each other,
we were young, oh so young. I'm sorry, but I just don't like this. Instead of repeating 'young', I would suggest to try to find a different word to explain it. Maybe... naive? It seems to me a few words in this poem are there just to keep the rhyme. And in some instances, that's perfectly fine. But I think you can still keep the beauty of this poem without rhyming every stanza. Some people will nag you for it, but who cares what they think! But this is just my opinion. It will still be great if you keep it like this.
Feelings that I was not important
engulfed me in thoughts that I was not enough. Using both 'feelings' and 'engulfed' here don't sound quite right to me... maybe replace 'engulfed' with sprung? And perhaps say, 'Feelings that I was not important/ Sprung thoughts that I was not enough.'
but accepted the fact that she did not care.
Attacking only her, or else my soul would just melt.
like she did in the past.