I can't really critique this much, there's no rhyme scheme to analyse and the subject is very personal so I will keep my comments to a minimum.
The fact that this doesn't have rhymes doesn't mean that it doesn't have a structure of course. There are all the "When I" and "I saw" anaphors in the first couplets and the "What I have always seen" (an entire line) and "Is the" anaphors in the second half; there's also the "you" epiphora in the first half. In fact, you ended up using a symploche in the first couplets: "When I... you."
As I also mentioned, the poem is clearly divided in two halves; three couplets, "Now/I see/is everything" couplet, three couplets, "I see/now/Is everything" couplet. With this in mind, the first of the two poem-dividing couplets doesn't convince me that much. The ellipses seem unnecessary and the "Now", if you wanted to create a symmetry with the ending couplet, should go inside the couplet, not on a different line. Having it alone on a separate line does create more emphasis, I'll give you that, but then why not do the same with the final couplet? There's also the fact that that's the only case in which the "Is" phrase is on the same line instead of starting a new one. What you could have done is "Now/ All that I see/ Is what means everything to me", this way you keep your emphatic "now" separate but you dump the ellipses and start a new line with "is", keeping the general structure. As for the final couplet, you could have then similarly divided it into "Now/ What I see/ Is everything I need". This is of course just my personal preference and opinion, you didn't make any actual objective error so you should ignore it if it isn't what you wanted for your poem.
As for the subject of the poem itself, well I can't say much, it's a personal feeling. I thought the "Now" signalled a change of opinion (e.g. the narrator didn't love their SO anymore) but instead it just gradually magnified the sentiment. It's a confirmation of one's love over and over; it reminded me of a marriage vow tbf.
Well this is it, it's filled with personal preferences and suggestions instead of being a correct objective review, but it's difficult to do that with poetry, and with this poem in particular.
Edit: this turned out longer than expected, lol.