<human>: I'm with my gf for 4 years now. Everything is great, our life is awesome and we are having plans, etc. Sex is great too. I feel I love her. I mean, I still smile everytime I see a picture of her, and feel the love rushing through my stomach :) But, in the last period, like in the past few weeks, I feel an increasing desire to pick up others. Not exactly just the sex, but more like the "thrill". You know, that dance, where you are getting to know each other, you know you like each other, feel the increasing fire between you...The lean in for the kiss, this stuff.

So, I was in a party with my gf but she left early and I had a great time with one of her girlfriends, and ohhhh the excitement and the chemistry....*I can't get her out my head*. I can't really describe it more.. 

I feel terrible, because I don't want to like this. And I don't understand it, because I feel the same when I'm intimate with my gf too. Its just in the past I noticed the attention of many other good girls towards me and I'm confused about what should I do... Before her, chasing girls and stuff like this was also a big part of my life, so its hard...

*I know I'm a dick

Can you summarize the given text in a few sentences?
<bot>: Have a great gf of 4 years, good life plans with her, I love her, but really missing the thrill of the other girls. What should I do?