Hi there,
You don't really talk about depression at all so I wonder what made you post here?
What you describe is a slow decline in your confidence to a stage where you are starting to think you are useless. Which, of course, you aren't, you have 2 children and are both a Mum and a partner. That's success. If you incapable neither of those things would have happened would they?
I suspect that what you need is one of those courses that allows you to recognise your abilities and be able to use them. Assertiveness skills. Try at the college or uni for courses of this type but certainly see a counsellor for advice ands guidance on improving your self image.
Believe me, very few are comfortable at interview and being nervous is not always a problem for the panel. What's important is your application and references as interview situations are unnatural and not to be used to judge someone's ability.
Look ahead, not back, and see where you might be in 5 years.
depression can come though many different thoughts that you might be thinking.. if you have been dealing with this for years you should now try seeing some one who can talk to you and give you a better understanding on what it is that your going though. my advise to you is to start writing down your thoughts when you feel like its to much to bare, then rereading your writing and think to your self ways and ideas to keep your self away from these issues that seem to upset you.
as for the idea that every thing is going to go wrong try thinking postive thoughts and focus on good ideas or people in your life. you speak of having 2 kids and a bf which is something postive. and if you dont want to mess up the relationship start something that will keep you busy tokeep your mind off of things. like lil project around the house, volunteer work or helping others.
Major depression has many levels of severity, but if your depression is bad enough to where it is becoming a limiting factor in your life then you need to seek help.
If you catch it now then you have a better chance of beating it. Let it go and it almost always gets worse. When I say worse, I mean potentally far worse than what your mind right now can even imagine.