Ok this thread has stuck a raw nerve to me. I might be projecting there so feel free to ignore my comments.
NOTE: I am NOT the OP's DW....
I met my partner when I was in mid 20s. Just like the DW I was a virgin, so he was my first partner. It also happens that my partner has some social/communication issues so talking and especially 'sensitive' subjects such as sex doesn't come easily to him.
We had sex. It was sort of nice but nowhere mind blowing. After a couple of years it became tedious and boring. I never had an orgasm with him. It was all 'quick', I didn't have time to 'warm up' so to speak. He never said anything even though he knew I didn't have an orgasm. he just thought I had a low libido and wasn't 'into sex' aka it was all my fault and he couldn't possibly do anything about it.
The reality was that I had no idea what good sex was. I had no idea of what would turn me on, what I would like, let alone being able to tell him! And he never asked either.
I also probably didn't make it really nice for him either. He never said what he liked, his clues were poor and when I did take the courage to ask he just said 'you will have find out yourself'.
And so we went. I was frustrated, didn't enjoy it so avoided sex. Tension just went up and up.
Add to that 2 young children, me stopping working and being very isolated (all my friends were still working, I had no family around and no 'mummy friends') and him being away for work half of the week. That was a recipe for disaster.
Now I am lucky that my partner never put the blame onto me like this. He tried to understand instead. We worked through it, both us. Both on sexual issues (eg I learn to know more about my own body and fantasies and to talk about it. He learn to know my body and what worked for me, which wasn't automatically what worked for his previous gfs) and our relationship issues (eg balance between work and home for him and me).
And we pull through.
Some of the answers are leaving speechless. Apparently, the DW should just 'get on with it and give him sex'. Regardless whether she enjoys it or not?
She must not like sex or not fancy him if she doesn't have an orgasm/enjoys sex with him?
He is her one and only partner, she had no experience at all (and still has no experience for what good sex is), but it's OK that he has never taken the time to see what turns her on.
What my experience taught me is that having good sex is a two way thing and that he will need to put more effort into it if he wants it to work.
Then of course, you have all the added issues of the relationship as such that will also need to be sorted out. If the DW doesn't do anything else at all apart from looking after the dcs, there is an issue. If she feels he doesn't pull his weight, there is an issue. If she feels that he is pestering her for sex, there is an issue. If she doesn't/can't accept that there are some sacrifices coming with having a new business/being self employed, then there is also an issue.
And to want to have sex with someone, especially when the act itself isn't that attractive due to the issues above, then any small problems is likely to be a very strong deterrent. Unlike couples where sex is what 'bind them' and helps them overcome daily struggles, daily struggles makes anything to do with sex an even bigger struggle to 'get going'.
At that's wo talking about the fact she might 'have out the effort in', have sex when she didn't really want to and got very resentful for it.
Which takes me to advice to the OP that haven't come across.
Have you thought about counselling, both as a couple and sexual conucelling for the sex issue as such for both of you.
Some people can pull it out on their own but tbh it is much harder than with the help of a GOOD professional.