Vent/opinions needed😔

So i work as a clerk in a hospital- for about 8 months now. Everything was going well until I started going to the gym and people noticed a change. I wouldn’t say drastic but I lost weight and toned up. My boss kept asking me if I go to the gym and I told her yes. Now all of a sudden I get called out for not dressing “professional” ? She keeps calling my pants Jeggings and keeps saying she wants her clerks to wear a blazer but that’s not policy. Not only did she tell me all of this- she did so in front of several staff members. Now when I come to work with a different set of clothes on everyone notices me and says I look “professional” and they only notice what I’m wearing bc of her and one other nurse. My boss even pinched my pants to make sure they weren’t Jeggins. I had buttons on them they are just skinny leg like most pants these days (I got them from Primark work dept) . I’m wondering if I should go to HR or my union bc I honestly feel picked on at work bc it’s not up to her standards. Thanks for reading.

UPDATE: thank you all for your opinions. I have brought wide leg pants - let’s see if I still get singled out. Have a wonderful day ladies!! 🖤