Gaining

I've been with my girlfriend for over a year and I live her and knows she loves me. When I met her, I was really skinny but fit. I ended up getting abs and putting on some muscle and she liked that, but I later went from around 145 to 216lbs. I put on loads of muscle and also loads of fat. I loved it. And before that I had told her that I have a chubby fetish and that I would enjoy it if she were to gain. She is extremely skinny and petit and always has been. She didn't want to, then I went through the weight gain and she was nice about it, but I got it out of her and she said that she missed my 6 pack. I told her that I'll lose weight if she gained weight. She said ok. She's gained 7 pounds (she was 85lbs) but it's not really noticable, she's still underweight. I lost over 20 pounds of fat, but now I'm starting to gain it back. I just miss being big. I want to get to 250 and take it from there. But I don't want to be repulsive or unattractive to my girlfriend. I don't want her to have the urge to cheat on me or leave me. I've been cheated on plenty times before and it hurts. This one is really sweet, really religious, really pretty, and really smart so she is different and to tell you the truth, I want us to last. but I don't want to mess things up. I'd also like her to gain more weight but if she really really doesn't want to gain any more I don't want her to feel insecure about herself.
But anyways, any input on this situation is much appreciated.

idk in my opinion being sexually appealing to each other is an important part of any healthy relationship. i know people say that looks isn't the most important factor in a relationship, but as a girl who has a thin boyfriend but wants a bigger one, its hard if you're not happy in that department. and thats awesome that you want things to work out and you're both trying. but imo its really important to both be attracted to one another so in the long run you don't end up resenting each other/ cheating. just be honest with her.as dumb and repeated it may sound talk it out, see if a middle ground can be reached so everyone is happy.