Create yourself some 'you' time. Your missus does not feel sexy. She teases when there is no danger of you having sex because she knows this is 'safe' for her.
It is a bad habit.
Get someone to have the babee for the weekend. During the week before, help her to clean and tidy the house so she doesn't have a thing to do but relax and best of all, no excuse but to be with you. Tidy up the toys and put everything away.
Don't try to dive straight in. Go out on the Friday night, have a few relaxing drinks and go home. Cuddle up on the settee and go right back to basics. Remember when you were first together and played 'feel-me-up-clothes' for ages? Do just that. Instead of you chasing her, make her chase you a little bit. On Saturday...take her shopping, have some lunch. Do something nice - just like you used to. Go out on the Saturday night for a nice meal or something and then go back to you house. (You will already have created a space to relax in - you've been working your socks off all week right?) Do the same again...make her certain that when she and you are curled up together, it does not automatically mean that you want to get in her knickers (even though you probably do). You have to get her to 'trust' you again...sounds daft doesn't it? Play it cool. Even if she shows signs of wanting to...don't. Play up all you like...but no full on.
On Sunday, get up and make her a breakfast in bed. Get some of the woo factor back. She feels like a 'mum' and only a mum. She has forgotten that both of you need together time to just be lovers...as you were and hopefully as you always will be. Get the intimacy back and the rest will follow.
Now Sunday mornings were made for loving...having had a baby, she may not feel as sexy as she once was. But you have already spent all weekend making her feel like a beautiful woman right? Hopefully, she will have relaxed enough around you for you to be able to spend the day in bed...what you choose to do with the time is up to you.
You would have invested this time in her when you were first together. Never EVER forget to keep investing it. So many men do...and then expect women to be able to switch from mum to lover at the first grope.
Well I can tell you categorically, it doesn't work like that. I was always rushing around, tidying, cleaning...everything to get the house just right and with a baby, it can be exhausting. Don't underestimate exhaustion...it can be a killer for relationships.
I do hope it all works out for you. I admire that your first thought was for her and you, and not just fecking off for an affair.
It IS there in her...you just need to coax it out.