Help identifying which modules so I can reduce memory being used

I am using Apache web server and have installed a number of modules using their default modes, since then I installed a number of software. I want to reduce the memory used by the system and would like to remove some of the modules I have installed. However, I am not sure which modules are being used by the softwares installed. Is there a way to check which modules are being used so I can remove the ones that are not? I would really appreciate your help. Thanks.
