Everyone who wants to make a distinction between porn and erotica has their own (often eloquently stated) definition of what the differences are between the two. But go back and read everyone's definitions, and no two of them are the same. Where you draw the line is different from where the next person draws their line. One person's erotica is another person's porn.
There's a continuum of sex writing, from well written material that serves the plot and/or characterization on one end, to complete and utter shite on the other. If you want to draw a line somewhere down the middle of that continuum, and call the sex writing on one side of it "erotica" and the sex writing on the other side "porn" that's up to you. Just understand that where you draw that line is subjective. You will not, and can not, get to a universally agreed upon and accepted definition of what the differences are.
I write stories that include explicit, on-screen sex. I happen to think I do it reasonably well. But whether you want to label my sex writing "erotica" or "porn" is your issue, not mine.