Only way this ends well is if you are bi-sexual and you both spend time pursuing other women. Relationships seem to be able to handle an extra women or three, but an extra man is disaster. Not saying it right, wrong or otherwise but just the way it seems to be.
Your pre-baby relationship ends the moment you take your baby home. The longer you pretend your pre-baby relationship should still exist post-baby the more pain you are causing each other and your daughter.
You either learn about each other as parents (instead of individuals rocking out in the no-kids universe) and find that you can fall in love with the new person you're suddenly cohabiting with or you move on.
Polyamory is a nice idea but a complete nightmare unless you were raised and live in a community that practices. You seem to be seeking validation sexually, probably because your partner's sex drive or attraction to you has dropped off the map.
This isn't going to change any time soon. Men's testosterone levels fall through the floor when they become fathers. Your home is becoming a shrine to your new child and everywhere he looks something reminds him of his daughter. It's not sexy and it's not a place he wants to have sex anymore.
You're a beautiful woman and most any man would drop everything to hop in the sack with you. But sex and parenting are horrible bedfellows.
Best advice is to take a three day weekend as soon as you can, without your child. Get drunk, high, dance, fuck, eat repeat. Then go back to reality.
Hit the nail. Thanks for your comment I really enjoyed it!
And I enjoyed your post, thank you for being so candid. Looks like we are about five years ahead of you guys and have gone through many of the same things. It's hard and gets harder as the routine sets in. Parenting can be summed up as "No said it would be easy, no one said it would be this hard." Flip side is, until you become a parent you haven't really lived. So there is that. Best of luck!
Wow! Great comment! good way to look at it.