I just felt like I read parts of MY life story as well! I was skinny as a child, but at puberty the weight just seemed to go up..and up...and up. I haven't been in a relationship for a long time, and have often felt invisible. To combat this I developed the 'big girl' personality. Funny, sarcastic, witty, etc. Apparently I use it so well that my closest friends didn't even realize how much I hate this body that I'm trapped in. When I found out about the sleeve I almsot started crying from relief. I'm hopefully getting sleeved in April and I imagine my emotions will go through the same roller coaster ride as yours are. All I can say is that you're not crazy and you have a right to feel how you feel. Repressing those emotions would be bad in the long run, but maybe you can channel it into volunteering, running, a new hobby, etc. All of those things can make you feel better about yourself and help steady your emotions. If there are any support groups in your area for post-sleevers, then maybe you can try and go to those. If nothing else, you'll know that you're not alone in how you feel.
Good luck and keep us posted!