<human>: Can you condense the text into three sentences or less?

This is my first real long-term relationship, and I'm very attracted to my girlfriend, but thoughts/fantasies of sex with other women have been entering my mind more often lately. We moved in together a few months ago and things continue to go great. I'm usually very open with her about just about everything, but the idea of saying, "hey, I had to jerk it this morning to thoughts of banging an 18-yr old asian girl while you were in the shower" are just not something I can ever share and it makes me feel a little bad that I'm thinking like this.

I don't know if it has anything to do with it, but I'm very into fitness, and when I met her she was about 15 lbs lighter. She put all of the weight on when she was going through some emotional issues due to a loss in the family around 6 months ago. It sounds shallow but I know that I'm somewhat less attracted to her because of the weight. She 'talks' about working on it, but she'll eat healthy early on in the day, then resort to eating half a bag of candy at night and basically hasn't lost any weight in the last several months.

I don't know if it's partly the honeymoon phase wearing off, the weight, or just a combination of the two, but I find myself looking at porn more often and imagining myself banging these other girls. I feel a little guilty, but then part of me is like, "well she hasn't really been doing her part lately and as long as we still make love 4-5 times a week then I'm not doing anything 'wrong' by having fantasies." Still, I know for a fact that it would bother her if she knew I was looking at porn sometimes and jerking off. It's not an every day thing, more like once a week, but it almost feels like a treat when I do it now where before I would _always_ prefer sex.

Is this normal, or a symptom of the weight gain and subsequent lowered attraction?
<bot>: I've started to jerk it to thoughts of having sex with other girls, feel a bit guilty about it, and not sure if this is normal or whether it's a symptom of GF's weight gain.