Well, welcome to the roller coaster. Hop on and enjoy the ride, you will be here for the long haul if it all goes as it usually does
Take a breath and realize that this is a beginning. I agree with NYCindie, she had her world rocked today and sometimes people respond with "Oh ya, well let me rock your world too sunshine!" Don't take it to heart, I would be very surprised if she ended your seemingly long marriage, if in fact you kid is yours, from one conversation....
I think the advice here is pretty accurate, you should take it
and come here for comfort, or find a group there... take baby steps and be persistent that this isn't going to change for you.
Do you get to have a girlfriend tomorrow? No. I hope you don't have anyone lined up or you will be shit out of luck. Do people start out this way and end up being able to get their needs met? Yes. Quite often it takes time and life changing work, but it is possible. You have made a really good start it sounds like; honesty, respect, openness, no cheating... consideration and compassion could use some work, but meh, its the first day... you'll get there...
Some suggested reading would be under the tag search of "foundations" and "lesson" go to the tool bar and click search and it will direct you from there.
Good luck with tomorrow. Take a day at a time and remember to breath through the hard stuff.