Well, Okay, where to start..
When we got married, our sex drives never matched up completely but at least we did it a few times a week and she seemed into it.
So it started out wrong already..
Now that we’re older with a couple of kids, sex sucks.
That's normal.
You don't marry and get kids to have a freaky cool sex life.
That's what they might tell you, but the truth is that marriage like starting a small company, where you are partners and the children are your product.
If you thought you would get a steady source of hot steamy sex because you married here you were exactly doing the wrong thing.
I initiate 99% of the time, and she rejects 99% of my advances. I feel like I have to whine and bitch to get sex and I hate it.
And that's why she rejects your advances.
Something that you can readily have all the time is not desirable for most people.
If something is shoved down your throat (literally

), it's even becoming reviled for someone.
Your wife is not any different here..
We only do missionary cause she refuses to do anything else and lately she even hates to kiss.
Dude, that's a major alarm sign.
Frankly I think about leaving all the time but I’m ugly so I don’t have tons of other prospects.
Yeah, but what are your "prospects" here?
I mean, if you are happy with her otherwise, and she is a good mom to your children, you can decide to keep the marriage afloat.
Just don't think you will ever get her to be the wild sex beast you'd like her to be.
That won't happen.
I’ve considered escorts just to scratch that itch, but she handles the finances so she would see the missing cash and ask questions.
It sounds a bit like she is the man in your relationship. You probably got betaized a big lot, and now you are wondering what happened.
The same thing happened to me as well around 8 years aho, and that was with a woman that was crazily jumping at me trying to hump me whenever we were one minute alone.
After having a kid and moving in together, and sharing a bank account, she suddenly "didn't feel like it" anymore. I was in the same situaion like you and wondered what happened, since I thought I did everything right..
The truth is, sex is not negotiable. She won't be hot for you just because you were "a good boy". It's actually the opposite. and that's really difficult to maintain in a marriage.
If I were you, I'd stay married for the kids, but search for other prospects actively.
If you want to read a bit up on this gender dynamics stuff, search for "the rational male" by Rollo Tomassi or, more specific for your situation, "the married man sex primer" by Athol Kays.
Also, get shredded.