All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad (saw) is His slave and Messenger.

If you are certain that you cannot give birth to children and your husband is desirous of children, then you may encourage him to marry another woman to have children while you continue with him as you are now. However, you are not obliged to force him marry another woman but if he marries her, it will be unlawful for you to oppose him or ask divorce from him due to this reason.

Allah knows best.  (Source: islam_web) Classified in Women and Family > First Steps to Marriage