Sorry you sound very low...and yes, YES you are definately suffering with depression!! I'm not a professional, but, I have had exactly the same type of thoughts as you, always when I am very depressed.
I use Cognitive Behavioural Therapy self help, which is really excellant. I've recommended it to everyone I've ever met who suffers with depression.
www.amazon.co.uk/Feeling-Good-New-Mood-Therapy/dp/0380810336/ref=sr_1_1?ie=UTF8&qid=1439039859&sr=8-1&keywords=feeling+good+the+new+mood+therapy
(this authors book is the most popular book for Psychiatrists to recommend to their patients)
here is the author giving a 'Ted Talk'
I can lift myself out of depression within minutes using the exercises (you write down your thoughts, identify the 'distortions' and write something more realistic, that you believe and this makes you feel a lot better!)
You are having 'illogical' thoughts which are causing you to feel very low.
Just because you do not have a job or children does not make you 'worthless'.
Nothing can make us worthless because we're not a 'commodity', it's impossible to measure a Human Being's 'worth'.
Obviously we all know that going down the road of saying one person is more 'worthwhile' than another, is a bit dodgy (taken to extremes is basically fascism!), you probably wouldn't say someone else's life wasn't worth living because they didn't have a job or children, plenty of people don't (I don't!), please don't think it about yourself.
Think of some people in society you've read about, or know, who have a 'successful' career, children etc, but are not particularly pleasant people, whereas you might be able to think of someone you know who doesn't have much money, career 'success', family etc but is a really nice person. Please don't compare yourself to others and judge yourself so harshly.
I have had, and sometimes still have, those exact same depressing thoughts of 'worthlessness' but change my mind with the CBT exercises...when I remember to do them! or I am in for hours/days of feeling very low.
The book above has so many great ideas for changing your thinking around, can't recommend it enough! As your mood improves, you feel your interest in life coming back, you want to do things, hobbies etc...depression is so awful because it causes a viscous circle of thinking..you don't want to do anything because nothing seems enjoyable or worth doing, then feel even worse because you are cross with yourself for not doing anything!
If you have got the point of thinking life is hopeless and are having suicidal thoughts..especially if you are making any actual plans to end your life... you really need to speak to someone who can help you, can you see your doctor? If you are feeling this low they might be able get you some help quickly.
Also is you are suffering with bad anxiety, you could possibly have a problem such as an over active Thyroid..this is what I was diagnosed with after several years of awful anxiety, that was resolved overnight with medication.
You don't have to feel the way you do at the moment, you can feel better 