hi janedoe
Relationship problems are rarely one sided even if its just one person facilitating the behaviour. You have been married for over 20 years so must be aware by now of your OH's personality, therefore I assume an acceleration in his negative behaviour have prompted your post. A few pointers to think on:
Could his finances be in crisis and he's hiding something, therefore pressure is bubbling and you are getting the brunt?
Are you feeling life is passing you by -mid forties perhaps,given up career to look after child and now feeling frustrated or bored therefore picking up on every little comment your OH makes to try and justify how you feel yourself?
Do you often have feelings that people are 'getting at you' or that life is throwing you one problem after another?
Is OH where he thought he would be at his age or does he feel as if he's underachieved and life is passing him by (mid life crisis)
Does the negative behaviour have any pattern -is alcohol a factor? This question is for you and your OH
Do you want a job or are you happy the way you are (excepting for your relationship problems)
I think you would benefit from relationship counselling but for starters why not print off you original post -show him it and tell him you need to talk.
http://www.relate.org.uk/relationship-counselling/index.html