Hello love, welcome to the club. Membership is not optional.
That's the bad news. The good news - you've arrived at a great place.
Firstly, I'd recommend 'Why does he do that' by Lundy Bancroft. He's an American Therapist - don't let that you do the eyes to the sky thing (I did) but it's still worth the read. It'll help you think about your situation. It has a very interesting chapter on men in therapy abusing their wives with psycho-analysis. You may find your DH's words in that book. It may give you some perspective on the inner voice that speaks to you, which he may be quashing with his personal insight.
Your marriage does not have to end with this. However, only you can make that decision. The chances of you getting over this in the short term are nil, in the long term possibly.
Whatever happens in your marriage, whether you continue it, or dissolve it - make the decision with your eyes wide open.
The biggest factor we all feel when discovering a DH is having an affair (sexual or otherwise)/or being abandoned without warning - is how the hell we are going to pay the bills.
Almost all of us are in the middle/or recovering from a critical period in our lives. Those of us 'in the middle of' are often buying a house or other significant commitment, those in the 'critical period' are recovering from a period of illness. That's my take anyway.
That's before we even contemplate the reality of divorce - and how that re-defines us as people.
Divorce is more about the financials than the dissolution of the marriage. That's why, if you can, the first thing (irrespective of your readiness to leave or stay in the marriage) you need to find a solicitor/go to the CAB. Most solicitors give an hour's free consultation if you leave in a city/large town.
Every divorce is different - so do not rely on anecdotal stories/press/family to tell you what it will mean for you.
Seeing a solicitor is not the same as committing to divorce. It just explains your rights, and those of your children, should that option be the one you choose.
It is not as scary as you think.
But don't hit him anymore. You could end up with an assault charge. That doesn't bear thinking about.
Many of us here say we want to kill our husbands. In fact, many of us offer to join a queue to kill each other's husbands. But saying it is okay, doing it is not okay.
Keep posting - there's a ton of women here that can help you.