Time to definitively end your relationship. You both don’t want to be together long term and know it’s not right. So it’s time to stop.
Is he your childhood sweetheart? So you are really starting from scratch with no experience? That can feel really daunting, understandably. And you will also experience grief as a major part of your life is ending. But truly OP, you will overcome this.
Yes, there will be a period of transition when you feel distressed and a bit lost. And likely some false starts and let downs as you rebuild. But you will grow massively!!!! You have a blank canvas to start designing the next chapter if life. I’m willing to bet you will realize you have lost track of who YOU are on your own without him. It sounds like you are quite merged if you can’t imagine not being with him. That means you can rediscover the grown up you. (What is your favourite colour? Taste? Where do you individually want to travel most? What are your core values? What do you most want? What gives you pleasure and a buzz? What are your desires?) Then there will be dating, when you are ready. Yes, there can be pitfalls… but there can also be amazing new people and relationships which can make you much happier than this one.
I had a massive breakup when I was 38. In terms of basic markers, much worse than this, as I was married, with a child, and he cheated. But maybe similar to you, as he was my furst real relationship and it was long (21 years for me). It was about 9 months of hell, followed by 18 months of self discovery (lots of joy and some remnants of grief), now followed by the seven happiest years of my life, settled emotionally, successful financially, much more my true self, and with a partner who is the right one to have at my side for the rest of my life.
I am hugely grateful for that pivot. Best thing that ever happened to me.
You have the chance for a pivot. Get rid of your cold, have a good cry, cuddle up and rest, then start the journey!