Loss of interest, decreased concentration and attention, feeling low and disturbed sleep or appetite are some of the signs of depression. Consult a psychiatrist who will assess you in detail. If you are feeling suicidal or hopeless, seek professional help immediately. Try some relaxation techniques like yoga, meditation and deep breathing. Indulge in hobbies. Spend time with people close to you.

Just like you have described your state of mind at different stages of your life and how it has been affecting your functioning, including now..... is what life is all about. Our current perceptions, thoughts, feelings and behavior are heavily influenced by experiences we have been through, the upbringing, environment, family genes etc. Now it is up to us as to how we deal with it. You got to work on your perceptions and the little conversations you have about world, future, yourself etc. Enjoy what is working in life and work on what is not working, without complaining about world or yourself. It's all about emotional intelligence of continuously adapting to situations. If it becomes a challenge, then you are at risk of developing depression where in your views would become biased and automatic focus is only on negativity of life. In this situation, particularly in light of your suicidal thoughts, I strongly suggest you consult a psychiatrist immediately. See your current experiences in the context of depression, which is treatable. Best wishes.