I'm not sure I have any real advice, but I can sympathise. I often feel like I can't really participate in their conversations because I am in a different circumstance from them and I feel like I don't belong.
I was talking to someone today about how sometimes we can perceive that someone else is in happy circumstances and their lives are working out, but we don't really know the whole story. Often their lives aren't as rosy as we think they are.
Jealousy pushes people away. Although I accept that it is difficult to see people seemingly fall into easy social situations, relationship and friendships without making any effort when people like us are facing a constant battle to fit in and make our lives work and jealousy is probably a natural consequence, I would find a way to counteract it and find positive aspects of your friends to focus on. Maybe you could meet up one on one for a coffee and that way you are sort of on the same footing.
I don't know what else to say, sorry.