I don't think this needs to be a SAHM thread per se and I'm not going to flame you, dovebird, because I feel sorry that you are so unable to see what's so good about your life.
We have an income that's a lot higher than yours, yet in unguarded moments, I catch myself afflusneezing. Usually this happens when we meet dh's older colleagues, who would have been able to afford far better housing than we have and live in hugely sought after areas in beautiful homes, when they were the sole earner. Dh does the same job and is at the higher level at a younger age than these colleagues, but times have changed and despite us both working, we won't afford a similar home for our family.
You have regular holidays, UK breaks and limited debt. You are in a hugely fortunate position. Yet there will be many, many people with more. Your choices are simple: look at the positives or go out to work.
I would also recommend looking into the science of positive psychology as opposed to "Chicken Soup for the Soul" type books - Martin Seligman etc here. His books are somewhat cringe-inducingly American, but there is a lot of sense in how this movement breaks down wellbeing
Positive affect (feeling happy, positive temperament, mood etc)
Engagement - how engaged you feel with what you do
Relationships - how sustained you feel by your relationships
Meaning - how much meaning or higher purpose you feel you get from your life
Accomplishment - how successful you judge your life to be
It is perfectly possible to do almost anything and have a very high degree of wellbeing if the way you view what you do tallies with some of these indicators. An SAHM on a pittance can be just as happy, engaged etc as a high-flying career woman and vice versa, individuals just "get" what they need from different outlets.
You need to think either
a) my lifestyle, what I am doing as a SAHM and with my family engages me, sustains my relationships, I feel it has meaning and higher purpose and I feel it is accomplishing something important
or
b) I need something more in one of these areas, and I may need to work or to make a change to our current domestic/employment set up to achieve it.
Simple.