What is wrong with my fella?

Hi reddit, tonight my cat started acting quite strangely, he is usually a very active cat and he likes to hunt and play... But it's all the evening that he looks quite nervous and he twitches and licks himself in a way that I haven't seen before... I went to the vet and asked them, they gave him a shot of cortison and a pesticide (to give him at alater time) and told us that he does not look allergic or with some parasites... Do you have any suggestion of what this could be, maybe just stress?