Pregnancy Jealousy HELP

I found out today my younger sister is pregnant. Neither her nor her boyfriend have a job and both dropped out of high school. They live with my mother who is currently barely making it supporting four kids at home as a single mother. They are both incredibly immature. I am INCREDIBLY jealous she is having a baby before me even though it is my choice that I am on birth control. I’m older, no longer live at home and have two very well paying jobs. I am also almost through with college. I know I am following a more successful path and this is my choice. However I don’t know why I feel so I jealous or how to deal with it. I was previously pregnant and lost the baby. Yes I know this probably sounds terrible but how I am feeling :( it also doesn’t help that had my ex boyfriend and I stayed together we were going to start trying to conceive ourselves next month. Our mom told her she wanted her to STRONGLY consider signing the baby over to me but my sister hasn’t mentioned it to me yet. I don’t know how I would feel about that either. I do want to support her but I don’t know how I can do that with how I am feeling right now.