Sister in law

So we have been trying for 2yrs nearly An then the sister inlaw meets a new bf an 16 weeks later she's 10 weeks pregnant 🤰 she hardly knows him An I am trying to be happy for them but I can't am so jealous.. 😒 am I been really unfair?? I don't let her see or anyone for that matter that it's affecting me.. An we lost our baby on the 22 December but my partner didn't want to tell anyone which I agreed as I didn't want the oh so sorry lark!! But now I am so scared that my face is starting to show a different side the smile is starting to fade An I don't want this to come between us all.. advice would be appreciated? 😐