Body Shape Changes For Better or Worse?

Ok I just wanted to blob about something that I find to be a major road blocker. Through out the years I continually lost and gain 40 or 50 pounds from life situations and giving birth. I am now finally more than ever ready to make a permanent life change. My question is that as I get to a certain weight my body changes and it not exactly how I see myself. Yes my physique becomes more tight I hate that I keep my curves but lose my butt!!! I like having a big hiney and like it! Probably opposite of many people. Yet, anyways when I lose it as I approach a certain weight it discourage me. I want plastic surgery lol but not going to happen cause my fiance loves me the way I am.

My thoughts is man I must be dumb to want to change myself but its something I struggled with years before I met him. I just want to know how can I learn to accept myself and not hault my fitness efforts once I get to a certain size and continue my weight loss efforts?

Any suggestions, ideas, or thoughts would be greatly appreciated.