Hey guys - I'm new here!
In January my cat turned 1 years old.

Recently, just in the mornings, he has been having awful diarrhoea... It is somewhat... explosive (sorry!). We haven't changed his food, and he's been going out for a good couple of months now. He has also stopped using his litter tray, he won't even pee in it, so monitoring his toilet habits is really difficult.

He went to the vets a couple of days ago for a booster injection, but the diarrhoea had stopped then (until this morning). The vet basically told us to watch him.

Is there anything else we can do? I really want him to start using his litter tray again so some help with this would be great!
Should we keep him in for a couple of days and see if he gets better?