Hi jmg1. I'm sorry to read of your troubles, and must add my congratulations to those of others here who can see what a good job you must be doing with your children.
I am glad you found mumsnet, you will find this website helpful and supportive in many ways, not forgetting the small things as well as major life situations such as yours.
I believe any parents with three children under five would feel it was a struggle, even if everything is going well, it is immense hard work before you even contemplate your bereavements and your own family history. So I take my hat off to you. Please try not to feel guilty, I guess anyone would if their partner committed suicide, it would be a natural reaction, but please...give yourself a break. It sounds as if your dp had problems not connected with you that caused her mental instability and you have enough on your plate without feeling to blame for that.
It is terribly sad, but this is the life you are in and far from feeling guilty I think you should be feeling proud that you have managed to cope for you children. You are breaking the patterns of you and your partners' upbringings and lovingly parenting your own children to a happy well-balanced childhood you didn't have. I can't think of anything anyone could acheive in their life which would be more important.
Some people believe in counselling, some don't. I am one of the former, I believe counselling and phsychotherapy can release us from unhealthy behavioural patterns and damaging ways of thinking which result from wrong conditioning by parents. For me it was like breaking a chain which had bound me and finding I could live a happier life, expecting as much as anyone else from it.
However, I do understand that for some people counselling feels as Easy describes it, raking up bad memories and feeling the pain all over again. It depends how you are coping. If you find your own way of coping and it is working for you, you are not battling depression, then who can say you are not perfectly fine as you are. On the other hand people with excellent coping skills can reach crisis point without really knowing, because they are so good at coping that the depression hits them suddenly, as happened to me, I had worn out my coping skills and suddenly floundered under an immense burden I had been carrying for years.
For some people just having friends to talk to is enough. You will find there are people on mumsnet willing to lend a metaphorical ear at most times of day, if you are at home and cannot get out to meet a 'real' friend.
I agree with what people have said about getting out on your own sometimes. We all need a break from our kids, to refresh ourselves, to remember that we were adults once! Even if you simply go for a walk, collect your thoughts, or go for a quick pint, do try to arrange something for yourself, for your sanity.
I also think that you need a good female role model for them, unfortunately your dp's mother doesn't sound so great, but perhaps a friend or neighbour who can do the more girlie things with them? When I was bringing up two little girls alone, my father and a friend were excellent male figures for them, so that they could grow up knowing what a husband and father should be like, and have the discernment to choose a good man for themselves when older. I have now been married for four years, so they have a lovely dad in their lives again.
I would delay the decision about moving, give yourself as much time as you need to think about it and I am sure the answer will become obvious to you eventually.
It sounds to me as if one day your kids will know what you have done for them and you won't just be a much-loved father, but so much more besides.