How to get comfortable having sex/being with someone smaller than me?

So, I'm about 5'8 and on the thicker side. Maybe a bit chubby if you will. But I'm pretty and am not insecure in that sense.
BUT the new guy I'm dating is about my height, maybe slightly shorter and a bit smaller. He's not super rail skinny, but smaller than me.
It is something I have a hard time with, but because of my own insecurities, not a lack of attraction for him.
He's very sweet and we get along and have great conversation. We haven't gotten very physical yet besides hugging and playful touching.
He's told me I'm pretty and he's one of the first guys I've dated that is looking for a real relationship that gets serious. So I know it's not like he isn't attracted to me.
But I feel big and weird. And I know I need to breathe because he's a genuine person I'd like to be involved with.
Anyone in/have been in the same situation and have any tips?
Updates
+1 y
Update:
Earlier today I meant to send him the link to a song and it was accidentally the link to the vibrator I just ordered. 🙃
How to get comfortable having sex/being with someone smaller than me?
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