Appointments schedule loading for ever


I installed the Appointments+ plugin on one of my websites, it worked pretty well until this week when many people started to use it..

My appointments schedule is loading forever, i also often have "out of memory" errors.

I have been searching for a solution on google for several days, i tried a lot of things like :
- increasing the php memory limit in php.ini, in wp-config.php etc..
- reinstalling the whole plugin
- deleting all others plugins
- disabling the google calendar integration

I can still access my backend appointments system administration tho.

Does anyone know how to fix this?

Thanks a lot