my sister...need advice

Sorry to vent once again but I am in a hard place right now that I don't know if I even understand. My sister is pregnant...due any day now and she has had some serious struggles (which have made me so worried about her.)
I have felt so jealous of her too...she is healthy..skinny...and pregnant with a little boy. I feel pathetic and alone. It is so hard that her and my mom can talk about what is about to happen but I can't include myself because..."it won't ever happen to me."
She wants me to be there for the birth since "i probably won't ever get to experience it myself." (her words) I know she means well and that she loves me but I don't think anyone could know how difficult this has been for me. How can I say that I can't come in when she has the baby when she wants me to so badly...she said that she needs my support. Emotionally I don't know if I can handle it though. Any advice? It has been a bad day for me today and I have felt like crying...
It is like I cannot focus on what I have right now and I only focus on what I don't have. I hate feeling this way...it is awful. It makes me feel like I am ungrateful! But i'm not... I am so grateful for my husband and daughter we were blessed to adopt. I'm just in a place where normally (if we could get pregnant we would be pregnant now again since our daughter is 1 1/2) but we don't know what our next step is... adoption again? Invitro? or an only child? I want to enjoy every minute with my daughter...and I feel as though I am but I want a clear mind and I can't have one right now with the situation of my sister....I feel so down any advice?

Finding Hope in hard times can be difficult. Pick yourself up, hang on an don't give up!
Your dreams can come true if you believe in them! Don't think that just because life didn't go exactly how you thought it would that it is too late. I used to think it was too late but looking back now... with my daughter we were blessed to adopt...just because she doesn't have my genetics doesn't mean she doesn't have my heart! Every part of her is amazing... she was sent to be an angel to me. She is more then what I ever wanted in children.
Wherever your journey takes you...You are not alone!