"Having kids is wonderful, and life changing, and rarely what you're prepared for," Gellar wrote in the Instagram post. "I love my children more than anything in the world. But like a lot of women, I too struggled with postpartum depression after my first baby was born. I got help, and made it through, and every day since has been the best gift I could ever have asked for. To those of you going through this, know that you're not alone and that it really does get better. And if you believe that postpartum depression should be covered by healthcare, please take a moment and go to callmecongress.com today, find your rep's numbers and let them know."