<human>: Could you distill the essence of the text into 1-3 sentences?

We have been together about four months. Everything is going great. My boyfriend is wonderful. So hence my username: It might be dumb but...

The other day my boyfriend turned to me after I made him laugh about something stupid and said to me, "You are my soul mate." 

I was kind of blindsided. I thought about it, and was like "You're mine too!" And kind of melted. I told him I had never told anyone that before. I haven't! I never believed in that sort of thing until I met him and got to know him. (Sorry, sappy and vomity, I know, but true.) He agreed and said he hadn't either, didn't believe in them before me, etc etc.

Fast forward to yesterday and we're drunk on margaritas, and he comes out with something silly related to that conversation, then proceeds to tell me how he had told someone that before.

Uhm okay? I don't know...this is probably a stupid thing to be upset about, but for some reason I am upset about it. I guess I just need some perspective or something on the whole situation. It left me feeling kind of like, wait but I thought you told me....? And if you tell people this then what makes our relationship special as compared to the last girl you told? And why did you even have to tell me this information? You could have just left it at the conversation the other day...

If I'm being an idiot, just tell me I'm being an idiot.
<bot>: boyfriend tells me seemingly very intimate and lovey-dovey thing, tells me it's shared just between us, turns out it's not. Am I being an idiot?