Letrozole and sore boobs

This cycle I'm taking Letrozole for the first time after 4 failed rounds of Clomid. For you ladies that have taken it have you experienced extremely sore boobs?!? With Clomid I'd get sore boobs after my fertile week and leading up to AF. On the Letrozole I started getting really sore boobs on the second day taking the pills. It's now 4 days later and they're still so sore I can barely wear a bra. Is this normal?!