Wasting A Life

I'm sure I'm one among millions to have this feeling. I'm 25, pushing responsibilities ahead in time and slowly losing all my interest in everything in life. My regular days are filled with thoughts of confusion, anxiety, lying to myself and others, avoidance of confrontation. I struggle to sustain an image of being "normal", ie. kind, calm, happy or just to pretend there aren't any serious problems in my life, which, in fact, is a huge heap of problems. I'm a coward and even afraid to kill myself and put an end to it all. I live with my mother and her friend, but my family has been a mess a long time ago. For every day they're arguing pointlessly and emotionally hurting each other, even if it's unintentional. I used to have a slight hope in people and my few friends, but nowadays I find it hard talking honestly even to my most loved ones. I have a complicated relationship with a girl, who has a bit better circumstances, but maybe socially and emotionally is even worse off than me. We know each other for more than a year now and I'm meeting her quite often, but only at her place (her mother's, that is). Usually her condition can also be best described as "suffering". I think I love her, but she can't love someone inconfident and uncertain as me, maybe we're just making it harder staying "together" - as we are not a couple, rather intimate friends - as I said it's complicated.
The reason I write here is a kind of desperation or a feeling of total hopelessness... I can't even express it or I don't care, being sceptical about any good consequences it will lead to.
I feel I'm dumber each day. Failures and misfortune seem to accumulate and it's harder and harder to simply wake up and face the day - I know already that I'll be weaker and less intelligent, accomplishing nothing but procastinating. I feel so stupid and helpless - in fact, I used to be the person whom people ask for help - I'm too afraid to ask for help of others and have a deep feeling of shame, thinking that I need help. Also, I think that there isn't anyone who could really help me. I know practically any kind of help will eventually push me towards the fact, that I'm responsible of all this, I'm responsible for my negative thoughts and such and I'm the only one who can solve this. So as I play this and hundreds of similar scenarios in my mind I finally end up doing nothing and depleting my energy.
I'm very introverted and shy and despite having many pals I am really a loner. Most people from my past think of me as a smart person, because I used to be good at studying and problem solving - but only theoretically. My knowledge is becoming obsolete and worthless now, I'm failing to finish university, even the BSc degree, yet I teach some MSc students in maths, physics and such. I'm very ashamed of myself doing this without the adequate background. I know that if there were real standards here, me and my "students" would fail. I'm dissatisfied with our education, all the fake images of quality that our teachers try to keep up. I respect their experience but I don't respect their hypocrisy - although I'm a hypocrite too. I'm very lazy and resisting when I have to study myself, the more important it is, the less I care. I'm really screwing up my whole career, haven't I done that already... maybe some day I'll make a fair engineer but certainly not a good one. I'm not passionate about it enough, I think, and it would be late to change.
At this age I shouldn't be a student and ought to be much farther ahead, working, being apart from the family house, sustaining myself but I simply can't advance. I think I don't really want to. I can't picture a bright future for me, I've lost faith in friends - they seem to have sold out their souls, working and all, living alone, being in better relationships but lacking the happiness or hope we used to share as children. Even though they seem much more passionate than me, being quite successful in their jobs, earning enough money to feel safe - I don't know if I ever will, and honestly I don't really care - I accept passively the worse fate for myself. It's really awkward - as if I've chosen survival instead of life...