<human>: So we are both early twenties and been together coming up to 4 years. And when we first got together she had very little confidence in her body or herself. I knew this and I am always trying to do as much as I can to boost her confidence. I love her and she deserves every bit of it and we have come huge distances from where we began in that respect, but there are still a couple of problems I don't understand. 

Now we had some issues a couple of years ago which led to me splitting up with her, because I did some awful things his it and got my head into a mess (which I deserved) she forgave me but I couldn't forgive myself, so we were apart for a little while. Until I felt I had grown up and then I saw her, I knew I had to try and get her back. 
Which I did and I didn't think anything hung over us, we have been very happy since. 

But when we argue (which happens very infrequently) she will often ask if I am bored of her and going to leave. Which I'm not and will not. In my foreseeable future I know I won't, so I reassure her and we work out whatever argument it is. But it worries me that some doubt is still left and I don't know how to overcome it. 
There is another level to this, if I compliment her body she will not accept any compliment, and just say I'm delusional or turn it back to me. I don't understand how a compliment can't be accepted?

how can I phrase it in a way that might get through a bit better? 
I've tried communicating with her in and out of sexual settings, and just generally showering her with compliments whenever I can, to make her feel good about herself. 
I'm a "fix it" kind of guy and I'm not saying anything is broken, but if I can improve things in ways I haven't thought of I would love some ideas.

Condense the text into a few key points
<bot>: I don't know how to compliment my girlfriend in a way that gets through to her, telling her how great I think she is or her body is beautiful doesn't seem to be getting me anywhere.