Negotiating an offer, is it too late? - 13 weeks in

It is the first offer in 4 months and I do not want to mess it up. The hiring manager was friendly and open.

Thanks for writing this out. I went through something close to it last year, 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.