Why can’t I be happy

Why Can I not be happy for the women who are pregnant. I lost my twins a little over 2 months ago and ever since then if any of my friends have gotten pregnant I start to resent them. I don’t want to do that, I want to be happy and experience it with them but I have this part in me that has to force myself to talk to them about it and pretend to be happy. I just found out a girl that I work with that cheats on her man and tricked her man while he was drunk into having unprotected sex and got her pregnant, he was very against having children. I don’t know, I’m just angry that even after trying for so long even before losing my twins that she can slip up once and boom she’s pregnant. Any advice to help heal I guess