Negotiating an offer, is it too late? - first time posting

It is the first offer in 11 months and I do not want to mess it up. I have a competing interview next week. Did it backfire?

Thanks for writing this out. I went through something close to it 11 months ago, and it got easier once I kept a simple log of every call and form.

If they say no, consider asking for something else, such as a review in six months.