No worries, you'll be fine. Really, I'm telling you, it just feels really weird when they fill up your uterus with water and when they let the water out. I don't think the water was cold, per se but I remember it just felt weird. The only part that was uncomfortable for me was the insertion of the catheter through the cervix, but even that wasn't unbearable, it was just uncomfortable. It's truly not that bad. In my opinion, biopsies are way more painful.
And even if it's a polyp, that's also not a big deal. I know there's always that thought in the back of your mind about the big C, I also worried each time! But it's so, so rare in women who are not menopausal that you really shouldn't worry about that. I was more upset when I found out I had a fibroid because they're a lot harder to remove and they grow larger and cause a lot more problems with heavy bleeding and cramps and stuff.
I'm sure you'll be ok. Even if you still have a polyp and it needs to be removed, you just gotta trust me when I tell you that procedure is a breeze. It's only natural you'd be worried but just believe me when I tell you that I've been through much worse and I'd take an easy surgery/recovery like that over any of the others any day. If you have to do it then get it done on a Thursday if possible and take off Friday so you'll have a full 4 days to chill and take it easy before going back to work. Technically you'll probably only need 3 days but I like to pamper myself a bit so I always take 4.
You'll be ok, you'll see.