Sizing help

I recently got a pair of Sadie boots in 7.5 after trying both the 8 and 7.5 in store. The 8 felt too loose, there was almost no “handshake” and my heel was lifting an inch or more. The 7.5 felt perfect in store. After wearing the 7.5 out for three hours, they feel really tight. The handshake is more of a squeeze and I can feel my heel touch the back of the shoe. They also feel really snug in the width. Did I get the wrong size or will they stretch?