Well done, beautifully expressed. 5/5 welcome to the site

I love you for so many reasons
Big and small
And all of them are wonderful.

^ I think that this is a good introcutory stanza, but it could sound even better if you word it a little different. Maybe you'd like to try this:

I love you for many reasons,
some greater than the other,
but all of them are wonderful.
Like this you you won't use "and" twiece during those three verses and it flows better too, but you don't have to change it.

Insert some punctuation because that will help the reader to read and understand your poem better, but now to the positive: I like the fact that you repeated "I love you" at the beginning of every stanza, but the last because the last is the most meaningful, to me it seemed that way at least. I think that the emotions you portray are very strong and captivating. Overall I think you penned a good poem, that would be even better with a bit editing.

Brilliant wright!, keep the magic on..