Flighting. Turning toxic, how do you manage

My husband and I have been fighting all the time to the point he just shuts down and I go from 0 to 100 in a second flat.

We have been together for 8 years and married for 4. We have 2 children. 1 is 3 and the other is 1.5 years old. I am a stay at home mum and he is a manager ( retail)

We have had arguments in the past but they were more misunderstandings nothing major and we have learnt so much over the years. Things started getting bad for us after my second child was born. I was diagnosed with graves disease ( autoimmune) problem that effected my thyroid, moods I became angry all the time, I would sweat constantly, heat intolerant and so on. I started Medication in march which I have had to change as they just made me gain 20kg in 3 months that's another story. Not to mention my husband will be having surgery in a couple weeks and we will be finding out if he has cancer

Anyway we argue all the time as we both are spent, overwhelmed with work ,chores, our health, kids life in general we have no support network who can help out and are just destroying our relationship in the meantime and leading us to think maybe we don't work and are not meant to be together. I get frustrated and angry when he is home and exhausted and tired and he get overwhelmed and angry needing space. We are both very much in love and want this to work but don't want this downward spiral where we keep

Question is how do you manage to keep your marriage healthy when everything is stacked against you. Like I mentioned we have no time to ourselves let alone the relationship. No family support or network who can watch the kids for a date