You're not alone and so many people have these types of thoughts at varying degrees.
Sometimes realizing that you are not your mind and you are not your thoughts allows you to not get too tangled into the depression. You do not deny the depressing thoughts, but you do not identify with them as being you. You are not your thoughts but the space in which they occur. So when depressing thoughts arise you accept them completely and watch them arise, remain, and then fade away. Eventually you see a distance between the thoughts/feelings of depression and yourself. You are not these emotions and feelings, but rather the witnesser of them.
And while you may have depressing feelings arise, that doesn't mean you cannot begin to cultivate some more empowering and positive thoughts such as feeling compassion and love for yourself and for others. Additionally, finding some gratitude in anything (the blue sky, sunshine, the fact you have eyes, appreciating a loved one, happy about a certain aspect of your health, gratitude for obtaining the physical human form), can be something you can cultivate.
Best wishes, you are not alone. And this wont last forever. Everything that arises will fade. You true essence is joy and that will rise up in you.