Stuck at 155-160lbs?

incircles_lp2

I am beginning to think that my body is at/or close to it's natural body weight. This is discouraging to me because I feel like I am still so heavy, even though I have very little body fat on me (mostly muscle). I am only 5' 5" and the lowest weight I am able to obtain is 155lbs! I was 140lbs at my lightest, and that was only for a couple years in my high school years. Even though I was 140lbs then, I am thinner now with muscle and I wear smaller clothes. I want to be 135lbs someday, but I am starting to doubt that my body will ever get to that point. I do not want to be unhealthy or too skinny, I just want to reach my goal weight! I workout a lot and I do very vigorous routines on some weekends when I go backpacking, snowshoeing, snowboarding and bicycling. Where am I going wrong? Most of the fat that I want to get rid of is in my gut, but it is really not that bad. I need some reassurance. Please help!!!