Can you explain what you mean by you were trying to get answers from other posts molly?
Look I'm not going to lie to you, this is going to be a rocky road and you won't always feel the way you do now - sometimes you'll feel a whole lot worse and at others, a whole lot better.
You've heard of the fight or flight survival mechanism and what you're experiencing right now is fight mode. Your instincts are to confront this situation and head off the enemy at the pass. At some point over the next few days, you will feel exhausted though, so do give into sleep when it comes and make sure your H takes up the slack when that slump arrives.
I noticed you said in your OP that the feeling that you couldn't live without him was unexpected. That's entirely understandable. He's been part of the fabric of your life for 18 years and you came to trust that he would always be there, but perhaps you believed that if it all went awry, you would cope pretty well. Your feelings might have shocked you to the core, that in fact you wouldn't cope as well as you'd thought and that actually, you love him more than you'd imagined. That can be frightening and a pleasant surprise in equal measure.
The sex you're describing has been coined "hysterical bonding" and there are complex reasons for this happening, but it is again very commonplace in these situations.
It forms part of the "fight" mechanism I've described above, it becomes a symbol of "reclaiming" eachother and at a time when nothing seems certain any more in life, it can be the one thing that is good and true, while the storm rages elsewhere. There is also an aspect to it that I see written about less, in affair recovery manuals, but I'll try to explain it here.
In a long-term relationship, many couples get into the habit of not really seeing their partner as a sexual being. Sex can become more about "making love" and less about eroticism. The discovery that someone else finds your partner sexually desirable and very attractive literally causes you to see him in a new light - and your libido goes through the roof.
For your H's part, it might be that despite you having regular sex, he had also stopped seeing you as a sexual woman with needs and I'd be surprised if during his affair and the long build-up to it, from first meeting this woman, he hadn't started to think about you differently. He may have cast you in the role of mum to the kids and even though you were having regular sex, I'd be surprised if he hadn't made some unfair comparisons with the OW who was playing the role of the sex siren and every man's fantasy figure
. This is the unfairness of affairs - all the while she was telling him how sexy and desirable he was, there would have been times when you would have complained that he hadn't put the bins out. In competition terms (because atm, some of what you're feeling is competitiveness) it is never a level playing-field.
One of the things I always advise a betrayed partner to do is to speak honestly about how your needs were being met in recent times. It can come as an almighty shock to unfaithful men that they don't have a golden dick after all and that actually, they had been failing to meet their wives' real intimacy needs.
This is all part of what Shirley Glass talks about in the book - affairs often occur not when someone wasn't "getting enough" from their relationship, but when they stopped "giving" to it. The challenge for you as a couple is to chart when your H stopped investing in your relationship.
Typically in a feelings addiction affair, or any affair that occurs in a "good" marriage, that under-investment only started after the affair partner loomed into view, but in order to understand this all properly, it's really important that you both timeline properly. Your H must tell you when he first had any contact whatsoever with the OW and explain what happened after that in terms of the various boundaries breached until this point. It's possible that he tried to create a gap to let the affair partner in, but invariably this happens subconsciously. It happens a lot to people who literally cannot feel romantic feelings for more than one partner at a time and even though your H insists that he didn't see the OW as a long-term alternative, in order to have the affair at all, he may have had to distance himself from you. You will read in the book about monogomous infidels, but there are enormous variations within this. At one extreme, the MI feels guilty and unfaithful to the OW if he has sex and happy times with his wife and at the other, he feels guilt towards his wife who wouldn't want to be intimate if she knew what was happening. MIs are never compartmentalisers.
This could be confusing for your H, who may have congratulated himself in recent months that he was managing to pull this off and keep his worlds separate without causing anyone any pain. The OW knew the score and he hadn't made any promises to her - and what you didn't know didn't hurt you. I expect he thought this would all burn brightly for a while and then when the summer was over, he and the OW would part amicably and it would be a nice memory in his dotage. At that point too, he would renew his efforts in your marriage, because even he can't have deluded himself that he had been fully present in your relationship.
The timeline is also crucial to you, because I sense you might be the sort of person who needs to make sense of what is a "missing chapter" in your life. Various events and incidents might be explained now that you know about the affair. It is very common for people to sit down with diaries and their spouse's phone bills and re-construct the entire period, until it makes sense.
It is actually vital that your H knows what life has been like for you in recent months, but do include the build-up, because however long this affair was in its "active phase", there would have been a period beforehand, when the work friendship started down the slippery slope towards an affair.
I can send you a chronology of an affair that you might find helpful, but I'd be interested in what life has been like for you.
Finally, what has your H told the OW and did you witness it? It will be essential to your recovery that she got the right message about your marriage and an unequivocal parting statement.