Is it bad that I'm getting tired of sex with my girlfriend?

My girlfriend and I before dating were party animals..i had sex with alot of women and got tired of that and decided to date. My girlfriend is absolutely gorgeous and i thought i would never get tired of sex with her. We've been together about a year now and have sex at least 3 times a day. It's gotten to the point where it takes me hours to have even one orgasm however she loves it because she gets to have like 3 or 4. I love her very much & that's why i decided to look into it, i would never leave her. Would it hurt her to talk to her about this? Last thing i want to do is to scare her into thinking that im bored with our love life...i just wish we could enjoy eachother more instead of lusting like crazy. Any advice on either how to talk to her about it or what i should do?