My boyfriend won’t let me get a dildo

So recently I’ve been wanting to try sex toys because I never have. I brought this up to my boyfriend and he did not like the idea.

He said he might be ok with me getting a vibrator but he’d be more comfortable if I only used it with him. I brought up how I kinda wanted a dildo instead of a vibrator and he said no.

His reasoning is cuz he’s scared I’ll like it more than him and if it’s bigger than him he doesn’t want it to “stretch me out” and sex won’t be as good for him anymore. But he has one of those pocket pussy things that he uses so idk why he won’t let me get something of my own.

Has anyone else had this issue? Does what he’s saying make sense or is he being unreasonable?