I don't think you are insane . I think its relatively common to have doubts about this - it seems to come up quite often.
I think the name you chose is lovely by the way! But there is nothing wrong with swapping the names around (or just calling her by her middle name), or adding a new name in.
I added a new name to the front of DS's name at a few months, as I was never happy with the original name. I am glad I did, but I still found it hard. It was easy to do, and hardly anyone battered an eye-lid, so the pressure comes from myself really. I obsessed over it at the time, and I find it hard to let things go. I love the new name, and am so glad it's his name, but I get cross at myself for getting it wrong, and a little at DH for being so insistant on the original name when it was clear that I wasn't keen. Obviously it was my fault too, and he was really supportive in changing it.
So I'd say change it, but only if you are sure that's what you want to do. Otherwise, give it a little time. It may grow on you.
I found it helped keeping the original name as a middle name, as we haven't taken anything away from him.