I'm not good with grammar, so I'm not going to say it's wrong. Plus this is a poem so it can be however the author wants it to be. I actually thought the cat pee was a funny touch, but that's just me.
the thing about a lot of my writing is that I know, completely, how to use "proper" grammar but I kind of like experimenting with different ways of writing something. I understand if it bothers you, though. It's not for everyone.
Sean definitely was my previous boyfriend to the guy I was with in this poem.