Site page load very slow

Hi all a Newbie here

Can anyone help, i have a number of sites running on one hosting package with Bluehosts but am having some problems with the sites running very very slowly to the point where they are unusable. I have contacted Bluehost support to see if they can help and they came back with the following response:

‘The server appears to be working normally but your sites are taking quite a while to load. You may want to look at your scripting and repair your databases to ensure optimial speed’

This is happening to all domains on the same hosting packaeg at bluehosts (3 domains total). I keen to learn on the technical side but not really sure what this means or how i resolve it.

Can anyone point me in the right direction please.

Many thanks in advance.

Duncan