It takes time to get used to new clothes. I'll wear new stuff for a short time at home to get used to how they feel.
Don't try a new outfit when you are going someplace where you can't take it off.
If you are on a budget you can go to a Savers or Goodwill where they sell 2nd hand clothes to try on. If something looks hideous but fits really well, jot down the brand or label. Then you can shop that brand or label for something that looks better. A brand or label is usually consistent in sizing. Before buying look it over carefully to make sure it isn't worn down too much or has other issues.
But, because I am XS or Size 2, I get better deals at Kohl's discount racks when I get to use a 30% additional coupon!
There are plenty of tiny clothes on the discount rack that doesn't fit normal people. Sometimes there are benefits to not being normal.