Maternity leave

My maternity leave is coming to an end soon.. but im not ready to go back to work as I would like to spend more time with my LO. The thought of separating with her after being with her everyday these past 2 months makes me want to cry. May I know how can I extend my maternity leave and how do I go about telling my boss..? Is spending more time with LO a valid reason to tell my boss that I want to extend my maternity leave? And isit silly to go on no pay leave to spend more time with LO? Also, just to check, maternity leave is counted by weeks instead of 4 months right? Thanks in advanced!