Hehehee. 'One month does not a monogamist make.' A North-Tibetan saying (If it isn't, it should be!).
Seems like you have been hit in the face with some real good NRE! You go girl! It might be your Fella has some weird monogamy mojo going on for him, but it could be as well that there is enthusiasm, some real good compatibililty and a millennia's worth of pent up lust you two have going on.
So you met him and the reptilian part of your brain went; 'Ooh, there's a caveman who sure smells nice! I bet our kids would have a real kick-ass immune system!'. Some cynical evolutionary biologists are hellbent on proving that NRE lasts usually from 6 months to two years because that is the time a healthy couple normally takes to conceive a child together. Don't worry, I bet once the reptile in you is happy with the baby-making effort you've put on this guy, you will be back to your usual slutty self!
Me: bi female in my twenties