Spotlight causing high CPU usage

13" MacBook Pro 2016 - 2.9 GHz Intel Core i5 - OSX 10.14.6

I noticed a little while ago that Spotlight was not indexing properly and not showing proper results although "mds" seems to be using about 70% of my computer CPU (which explains some CPU overloads whilst using Logic Pro X).

Have tried using terminal to stop, re-index etc etc but it always comes up with "Error: Index is already changing state".

Any help?