Hello Saffie,
This really is a sad write.

Right at the start, the reader is left thinking that this is about regret felt for a lost love: ".....we will always belong in the past" but lost in the most permanent of senses: "In fear of disrespecting his memory".

He laid bare his heart for you and his last wish was that you would do the same. The sadness here is two-fold: one, that by writing "last wish" you seem to be confirming that he died and two, that you possibly didn't grant that last wish - that you could never quite do the same.

"I wish we could go back to before we wasted away" - a great line here - very powerful in the context of the poem. Your love too, it seems, wasted away.

Then the line about walking away from the tombstone. This man is dead, and despite never being able to cement your love in life, it has been cemented in his death - ironic indeed. We never realise the chances we have lost until they are gone, do we?

Fifth stanza confirms that. You now feel - in his death - you could have offered so much more in life and while you had the opportunity: ".....I wasted the opportunity to have felt it more back then"

Then the heart breaking close of the poem: "so here is my apology."

A wish that he could hear you now, and maybe if you say it desperately and passionately enough, he can: "I really did love you Baby as solid as concrete"

At least you admitted it in the end.

A powerful write indeed. I hope you are well Saffie and all the very best,
Ben