I shouldn't have to explain... * bit of a vent*

Yesterday me and my husband decided to go to babies r us to do a registry. Of course I was asked if this was my first babies to which it wasn't. The guy helping us kept making comments ( not bad ones) about it being our second child. We've never done a registry before. Our first baby was a preemie born at 25 weeks after finding out I was pregnant at 22 weeks. The assumptions the guy was making about me knowing everything because this was my second child was making me uncomfortable but I feel like I would look crazy trying to explain that all of this was new to me. Same with my doctor and nurses. They keep assuming I know about all the testing and whatnots. I wanted to be able to experience all the things I didn't do with my first but every time I turn around I'm feeling uncomfortable about it because this isn't my first. I want to do the parenting classes, baby shower, and even have thing explained to me because I had no idea what a glucose test was when I first did it. Even my husband gets annoyed when I explain to him how I feel about the baby shower. My first was something kinda thrown together last minute when we weren't even sure baby was gonna make it. I feel like I shouldn't have to explain my situation every time I want to do something pertaining to this baby but I hate the looks I get. Not sure if feeling this way is wrong or I'm just being emotional as usual. But I've been trying to just do what I want and not care about what others think.