What you are feeling is entirely normal and I don't want to sound pessimistic, but you will be feeling like this for a long time. It's as well that your H starts reading about the effects of infidelity, because if he thinks that you ought to be feeling differently a month on, he's got a very rude awakening I'm afraid.
Most infidelity researchers and therapists have settled on someone feeling recovered and their normal selves again 2 years after discovery. Obviously this is an average; for some it's longer and for others, it's shorter. On this board, I have rarely come across someone recovering their appetite and joy for life in under 2 years.
Various things help with this process and you might find it helpful to know what happens for many people on a sort of timeline.
The first few months tend to be characterised by a roller-coaster; a few days of loving togetherness and optimism, followed by a few days of sadness, anger or despair - sometimes all three. Gradually, but only if you unravel the cause of the affair and your H tells the absolute truth and makes efforts to change in fundamental ways, you will start to feel more hopeful. However, this is a long process and it cannot be rushed I'm afraid. On the positive side, you can emerge from this with a happier, stronger marriage than ever before - and you will both learn a huge amount about yourselves.
You don't say whether you have posted before about this, but you say the discovery was a complete shock. There is an enormously helpful book that we recommend on here "Not Just Friends" by Dr. Shirley Glass and I would really recommend it, but it is absolutely essential that your H reads this too. Shirley Glass was a therapist who used a trauma-recovery model to help survivors of infidelity and it is going to help you rationalise your emotions if you recognise that you have suffered an enormous trauma. Like other traumatic shocks, you might have flashbacks to the moment of discovery and the intrusive images you describe about your H and the OW. This book deals with all these things and more. Reading it will help you to both to see that nearly everyone who has been in this position feels the same things.
You might also be feeling scared and anxious, because in the early weeks, it feels like all your safety has been taken away. The world suddenly seems a frightening place to be and this causes loss of appetite, difficulty sleeping, feelings of numbness or conversely, intense anger, irritation and sadness. At your stage, there can also be anger and incomprehension that the world around you has carried on as normal, yet this dreadful thing has happened to you. When you saw your friends this weekend, I bet you felt it was like an out-of-body experience.
Your H really does need to step up to the plate here. I want you to treat this as though you had been run over by a bus and cannot function as normal. He must therefore pick up the slack and treat you as though you were grievously injured. He must therefore take things on that you lack the motivation to do - because I can imagine right now you feel that mundane but necessary tasks are utterly pointless and your motivation is low.
Keep posting, because there are lots of people who can and will help you with this. But I can't stress enough how important it is that your H starts doing his own research about how you're feeling and how normal and longstanding this will be. He needs to know upfront that you are both signing up to a very rocky road, but the rewards can be enormous if you love eachother enough.