How to feel after a miscarriage *venting*

I lost my baby about a month ago. My sister in law is also pregnant and her baby shower is June first. Recently I’ve been so angry and mad for everything that’s happened. I’m dreading going to her baby shower but am basically be forced to by the in laws..I hate saying this cause I feel like an awful person but..I don’t see myself wanting anything to do with their baby. I don’t see myself wanting to see them when it’s born or wanting to hold their baby. I’m happy for them or as much as I can be happy for them right now. I’m just not happy about being an aunt when I’m suppose to be a mom..I feel like such a monster for even saying this and no one understands it. Just the thought of my sister in law makes me so mad and I know none of this is her fault but I just can’t help but be infuriated. Could really use some advice or anything that could help make all this more bearable or even the baby shower more bearable..