Et tu, tapeworm? 
But, yeah, like the other poster said, I don't think it's an issue of love. I think there is a real difference between respecting your relationship and loving your partner. I'm not trying to pump up the virtue of the latter or denigrate the virtue of the former. I'm just saying that I conflated the two for a long time when I never considered succumbing to temptation. Fast forward circa now and I can recognize how those emotions don't fit in a neat,little box. People have conflicting emotions about love all the time. If I chose to sleep with someone else, it wouldn't be because I was in love with them. If I left my wife before cheating on her, imo, that wouldn't be a sign of love. I don't think she would feel loved afterwards. It would be a sign of courtesy and respect. The type you might show a co-worker. Once again, not trying to make cheating sound virtuous, just saying that the feelings that lead up to it are more complicated than simply no longer loving your partner.
I'm not buying any of the other reasons mentioned in this thread why you shouldn't cheat. They all admit that you want to but say you shouldn't for some reason involving consequences. Fuck that. I'm saying if things are right then you genuinely wouldn't want to.
I see 3 possibilities for you:
1. Love gets eroded by day to day crap and this has consequences in the bedroom.
2. You're not getting what you want from sexual interactions with her. Maybe you have some weird shit going on. Maybe she does. Relax, we all do.
3. Love just doesn't last. If it solves the problem of lust at all it doesn't do it forever.
2/3 of these you could potentially solve. Only you know if it's worth trying to.
Or maybe you just like flirting. It's a fun ego boost.
There's no evidence that love is an emotion I'm capable of so I'm kind of guessing. Anyway, yes, you should respect your relationship. But you should want to, right? Not just respect it because you have to. If a relationship is some grim forced march then what the hell are you doing? Lots of people do that imo.