weight roller coaster

i feel like i am on a weight roller coaster and i dont know how to get off of it.  i start to loose the weight and i just dont know if i just get pulled down, just loose my motivation to working out, or if i just get depressed or what it is. it just seems like it is a constant thing with my weight. goes up and down and up and down and i am so tired of it. i try my hardest to eat healthy (i know i may have my moments where i dont but for the most part i do try my hardest) and i try to workout and like i said dont know if i just get pulled down or what but after a while of working out ( i can go a month of working out ) and then it is like bang i get drained of my energy. then like if i take a month of no working out i get that energy back. but i cant keep doing this. i want off this weight roller coaster. i want to be at a healthy weight and i want to feel better about myself. and i want to be able to go shopping for new clothes and not feel ashamed or embarrassed about how i look.