The thing is your not screwed . If you take the right steps ..
The g/f loves you and she will be with you but your not making it easy for her by being married you don't seem to get it . I don't understand why you are looking for baby clothes and engagement ring , baby names when your married your not thinking like a 40 year old your acting like a 20 year old .

I'm glad your wife at least knows but you need to be a man and say I love the other woman and I need to let you go , so you can find someone who can love you back .

Stop saying what you want to do and just do it . I know your scared to take that leep but if you don't love your wife then why are you with her ?
And why do you want to jump into another marriage ?
What is the rush ?
I think your lonely and desperate and don't know what you want your having a mid life crisis
personally you need to seek help and let both woman go .