My marriage is really over

So my relationship with my husband has been rocky for a while and we argue so much. I've been with him for more than half of my life and I'm only 34, so I honesty only know adult life with him by my side. He used to treat me with love and patience and empathy but lately it's clear he's had enough and he's cold and distant. He's left me again today and I know this time needs to be for good but the thought of being apart from him breaks me. I love him so much but we aren't making each other happy any mote. I'm heartbroken and don't know what to do. We have a mortgage, two kids and run a business together so it's not going to be simple at all.