Have another or not...

I'm 38 & my husband is 9 years older than I. He has 2 boys 22 & 21 from a previous marriage. We have been married 12 yrs and have 2 boys of our own. 9 & 4...I really would like to have another child however husband says he's DONE. I'm currently on the pill. He wouldn't leave me if it happened but more than likely he wouldn't be as involved. Thoughts?