Smaller clothes

I have quit drinking (8 months), quit flour and sugar (14 weeks) and am within a pound of my goal weight! The weird thing is how unnerved this has made me as I seem so small after having lost 30 (what!) pounds. I went shopping for pants yesterday and when the clerk asked what size, I said size 8. I could hardly look at her as I was expecting her to raise her eyebrows and say ‘are you sure’. I even thought of saying size 8 or 10, just to be more modest. So weird that I can really feel my brain trying to convince me I am still fat, that I should keep my old clothes ‘just in case’, that I certainly can’t maintain this forever.
I am trying to think back to other times in my life when I lost weight this easily and was this happy and try to figure out where I went wrong to gain it back. The thing is (no surprise) that I can’t remember any of that, I totally checked out during the falling apart phase, or maybe it was just slow. I am determined to stay present and keep doing this work, but it would be a lie to say I wasn’t afraid that this is just a passing fad for me. And my new body is so obvious and public, I think how embarrassed I will be when I gain it back.
Also, even thought I am at my goal weight, I feel like I have more to lose to get to my natural weight, I haven’t really hit a plateau. And that is scary, I am almost tempted to start eating more so I can keep from losing more weight. I am 5.7 and 146 so I know it wouldn’t be unhealthy. But why is it so unnerving?