A better me

Hello everyone,
I am new to this so bear with me. I am a mother of 4, one is my step son, he's 11, my other three are 10 years, 2 years and 18 months. I am 30 years old, 5'1" and I am considered obese at 160 lbs. I have really been struggling with my weight and my self confidence. I barely broke 100 lbs before having my first son, never went over 115 lbs after having him, but since having my two youngest son and daughter, I have had the worst time trying to stick to diets and exercise. I find myself often depressed, unmotivated, and tired. I want to be that happy energetic mother that I want my children to have, but I find myself sinking into this pit of consistent "maybe tomorrow" or "I'll start Monday." I need this. So I am trying one last time to get my life back. So any and all help is welcome and very much appreciated.

Thank you
T