It is overwhelming and must feel awful, and going to a real psychotherapist would be very helpful. Yet for the start, I would suggest you taking a piece of paper and breaking it all down to elements- what happened, your emotions, the outcome and what's next.
For example, you are likely to feel stressed for several reasons: first, because it was a breach of your trust and sense of safety - a situation in which any brain would be stressed. To get some relief you could introduce nice little routines to your life - so that your brain feels more stable.
Next is a fact that a very close person physically left you. Here you need to fill in the space with other people on regular basis. That could be exercising with a personal instructor, taking any sort of private lessons. This would make up a little for the absence of care and contact.
Another thing is realising that you need two to tango... What happened to you happened to many people who didn't trust their senses. You should learn to trust your gut and don't get close with the people who make you feel uncomfortable. You should care more for your mental health and happiness, even if your senses are mistaken. 'I feel wrong/weird/unstable around this person' is enough reason to leave them.
Yet, neither should you be paranoid about your partner's dishonesty. And for that you need to be confident in that you are capable of building great relationship and you are worthy of love. You need to find that sweet spot where your life is full of wonderful things and people, and not just your partner. Then letting go wouldn't be that devastating and you would not let bastard persuade you again and again.
To sum up, I would like to cheer you up here. You are free now 😊 Free from a rotten relationship, which could have lasted years longer.. making you more and more unsure about yourself, unstable and unhappy. Yes, you spent many years with this person and it feels like failure, but hey, many of us been there (me included ;) and there was something good about your relationship, so you are not a dummy.
Just get that back straight, learn from your mistakes and let go. 7 years is enough and he used all the possible chances to make you happy. No more mercy. Take care.