TTC and not happening

I seriously don’t understand how couples that have been TTC for quite a while can get on here and see all these pregnancy announcements and not break down in tears. I’m just talking for myself but I honestly want to cry and sometimes do when I see all these announcements. I know I should be happy for them but honestly I’m not. My heart breaks not for them but for myself. We have been TTC for four years and the doctors haven’t been able to find anything wrong. In a way I don’t know if that’s a good thing or bad. If it can happen why hasn’t it?!? I am trying to stay strong and have faith but my faith is dwindling and I want to keep praying but what’s the point. Hasn’t made any difference up to now. My biggest fear is that we won’t have kids of our own and that breaks my heart in so many ways. And that fear gets bigger with each passing month when I find out I’m not pregnant. When I start my period I just wanna hide and cry until it’s over. That whole week is just a constant reminder that I’m not pregnant and maybe never will be. I seriously don’t know what to do anymore. I’m tired of wanting a child and it seems to be happening for all my friends and not us. I don’t want to be angry at God and I know I shouldn’t but a part of me kinda is. Anyone have any advice on how to occupy your mind so you don’t think about it so much? I think about it constantly. I pray about it multiple times a day. One of my close friends is expecting now and that is just making it that much harder for me. I just want to be a mom. And the ladies that are able to get pregnant with no trouble will never understand that struggle.