How am I supposed to feel?

Well I lost my baby to miscarriage about a month ago. My first pregnancy ever and it has hit me pretty hard. How am I supposed to feel with my best friend (who was so happy for me getting pregnant before even though she has been ttc for years) when she shows me that she is over two months late on her period and has a very faint line pregnancy test from three weeks ago? I want to be oh so happy for her and tell her how great it is that after all these years she has hopefully conceived (she doesn't wanna believe it yet so she is waiting to take another test), but all I feel is despair and grief and honestly anger.....i don't know how to adjust my thinking when my body is just now starting to go back to how it was before cycle wise and everything...