Whats wrong with him?

The guy i've kinda been seeing keeps being really playful with me like when we're talking over text. We basically put each others faces on things that look stupid or just are funny and it's been a while since we've done it ( we always loved roasting each other) but, today he did it for the first time in a long time which made me laugh and felt happy to see so I did it back and he put " stop pls" and I don't understand... ( we've known and been seeing each other for a good few months) and he's just being so hot and cold with me. Like he'll be really playful then in an instant go cold.