PLEASE HELP

Me and my girlfriend have been together nearly 2 and a half year now but over the past year we've experienced problems with sex. It's to do with me. I can't put my finger on what it is, but this isn't good enough. We both want to have sex but now she feels that I don't want to because I don't initiate. I have said I'm going to change so many times this is because I genuinely want things to work out. I love her so much and I know she loves me.
I've become quite self-conscious about how I look cause I'm heavier than she is.
And I have been slipping in and out of depression over the past while :(
I know I need to make things work to stay with my partner otherwise she'll go elsewhere for sex which would break my heart.
How can I tell/show her things will get better before she leaves me??

HELPPP

Have you talked to her about how you feel about yourself? If so has she in turn reassured you that she loves you the way you are?

We are all conscious about ourselves from time to time. Some more often than others. Whenever I find myself in that mood, I pin point what I dislike and try to change it. When you make an effort to change, your lifestyle/habits would too in the course of doing so. This may catch your partner's attention an initiate the talk (should you be clueless as how to begin).

Surely she would then share with you her views, whether she deemed the changes necessary. Seeing that she is with you working things out, she most likely loves you as you do her! Hopefully you may regain confidence with her reassurance and come out of your depression completely.

In short, communication would be vital to solving your relationship problems. You need to let her know what's going on inside your mind (it is impossible to guess one's mind in case you have yet to try). Open up and share with her. The ability to do so differentiates humans from propagation-oriented creatures in the animal kingdom. This exchange of thoughts and feelings makes us romantic beings.