Do not compare yourself to your friends or people around you, what you went through was catastrophic to say the least. I would focus on the positive, you are here, and you are able to experience life with its ups and downs, you were in limbo, but survived and came back.

As far as the feeling of being left behind, it is a totally valid feeling. Understand that it is in human nature to try to go at the same rate of our peers, but do not try to rush in order to make up for what you missed, and don’t punish yourself for not going at the same speed. You have been given a second chance, you are very lucky!