Your shopping trips sound exactly like mine. I try everything on - nothing fits - I buy something, anything, in sheer desperation, and go home quite convinced that I must be deformed as I'm obviously the only female whose body is such a strange shape that nobody makes garments to fit me. I then put said panic-bought article in the wardrobe, possibly trying it on once or twice over a few months, realise it looks hideous and off it goes to the nearest charity shop.
I have a new rule. If I see something I like, I try it on and IF it fits, I buy it, whether I need it at that particular moment or not. I am now the proud possessor of three tops that actually fit me and look good on. the fact that I have nothing to wear on my nether regions doesn't worry me at the moment. One day................