Should I negotiate my severance? - 12 months and counting

I was offered 3 weeks of severance after 3 years as a janitorial supervisor, and I have a few days to sign. There are 3 people counting on me, so I am trying to be careful. There is a non-disparagement clause. Should I see a lawyer?

I asked for two more weeks and a neutral reference. They agreed to the reference and added a week.