I am having thoughts of harming myself when I get low, what can I do?

I have suffered from depression and anxiety since I was a small child, my parents took me to a counsellor when I was 9 for the first time.

Over the years I have had what I call episodes, some worse than others.
I have thought about hurting myself, i dont want to die but i feel like i cant go on feeling this way.

I am so tired but I cant sleep, my whole body hurts, I cry all the time.
when i feel like this i think of all the things that i know have made me anxious since i was little.
I dont know how to move on from these feelings and make them go away.
I have 3 children and a husband, i have by all accounts a wonderful life but I cant seem to get happy.
I want to stay in bed all day and i pretty much have been for the last 8 weeks, i havent been to work and im relying on my husband to do so much and pick up my slack.
I feel like a failure, im letting so many people down incuding myself.
I feel so ashamed of myself and im letting my kids down, I love them so much!
If i didnt ave them i would end my life so that Ii could stop this broken feeling.
Thats how I feel, broken on the inside.
I'm scared to leave the house unless im with my husband, I have been taking him to the doctors with me just so I can go.
I was on lovan for 5 years, they have now put me on Cymbalta…they started me on 30mg and then a week later when i was felling even worse they upped it to 60mg.
They have given me valium 5mg to try and deal with the anxiety and to help me sleep but it does nothing.
I've tried taking 2 at night to help me sleep but i still dont sleep properly.
I have been trying all the different thing the pyscologist's have told me to do over the years, breathing techniques, pushing bad thoughts away ect.
They dont work!!!!
I have only been on the Cymbalta for i think 2 weeks maybe 3 weeks, my days run into each other.
I am so unsure of myself and scared I'll never feel better.
I hit a low point this weekend gone, I had spoken to my mother whom i have a lot of issues with from when I was young.
She made me sad and angry and i just want her to say sorry and admit she was wrong but all she does is deflect and put it all back on me but thats not far i was just a little girl.
After i spoke to my mum i had to run and hide in my room because my little boy was, he is 10.
I didnt want him to see my cry, my crying became uncontrollable i had closed and locked my bedroom door but he must have followed me and he heard my crying, I began to hit myself in the head and slap myself.
Im so ashamed because I know that its stupid to do that, but at that very moment I just wanted to not feel the pain in my heart.
Zach my son knocked on my door and was crying and asked me if I was ok.
It broke my heart, how could I make him feel bad???
I feel like a terrible mother, I never want to make my boys feel bad or worry about me.
He said he could hear me crying and that he thought i was throwing things but it was me hitting myself.
What is wrong with me and why cant i be stronger for my boys and my husband?
They love me so much and love them so much.
Its not fair to them, im trying to get better but it feels like it getting harder.
Is there a hospital or retreat, somewhere I can go till the tablets work and I feel better so that my children and husband dont have to see me like this all day everyday.
All I want to do is lay in my bed, I dont really watch tv or read or sleep i just lay there with my eyes closed.
Please help me, im scared?
I'm rostered on to go to work tomorrow and I dont feel like I can do it, I work in a busy shoe store in Chermside.
I have to speak to people all day and act happy and excited I havent got it in me….what do I do?
I dont want to let them down either?
Please give me some direction?