Don’t know how to feel

My sister in law is pregnant again. I’m so happy for her! Like really really happy for her! But I can’t help but feel depressed too. I really would like to be pregnant again but I know I need to wait until I get through school. Ever since my son was still born and I miscarried my second pregnancy I have been obsessed with anything pregnancy related. It doesn’t help that we were both pregnant at the same time when I miscarried. I feel like I’m going crazy. I feel crazy for feeling the way I do. I have an iud and I know I’m not pregnant but I took a pregnancy test anyways after finding out she was. I know. Crazy right? Me and my SIL are both 21. Also, I feel like I have never had someone I can relate to. Someone who had a child that was stillborn in the third trimester at age 18. It was so traumatic. I know other people have suffered the same tragedy but I feel like it is a different experience when you’re so young. Your parents and everyone else didn’t want you to have a baby and you feel like you’re supposed to be happy for the way it turned out. But of course that’s o the case. I feel like I’m always fighting with myself in my head. Im sorry this is all over the place. I have add so it’s hard to write. Please if anyone is a psychiatrist/ therapist/ psychologist please respond. Or mature, wise women. I need opinions.