2 parts of this post required for you dd...
1] Study Group
Collective minds can help resolve all sorts of issues whether you are knowledgeable or just grappling with concepts. Beyond being sociable, offering support or asking questions is contributing to a common objective: understanding.
The spin off from this, at your discretion, can be the seed to more fulfilling social interaction as you find shared interests and new discoveries - it takes time... and practice.
Having a chat with a paediatrician sounds like a positive step. As you point out, your imagination can work against you where that inner voice rules autocratically.
2] Parental influence
Yes, time is fleeting and we all live until Nature or Fate decides that we shan't. 'Ending it all' (but not in quite the same terms as your reference) is actually something we do several times throughout this journey -
> we 'end' our childhood when we dispense with toys,
> we 'end' our reliance and dependency on our parents for support and nurture,
> we 'end' living as self serving and materialistic... well, I guess that one takes a bit longer to achieve. Such are the stages of life.
Christians believe they need to be reborn for everlasting life, which is much the same thing as shedding a previous way of life; Hindus believe they will be reincarnated as life is cyclical and eternal (although how they live factors into this); Ancient Greeks believed that life served to grow the soul.
Struggle and suffering are part of the process, just as exercise/physical exertion gives you muscles - I guess the feeling of accomplishment mimics the emotional development found in everyday interactions.
You are correct - we are here for as long as we are meant to be, but that meaning and our very reason for enduring, lies beyond our conscious mind; and the impact you may leave on the lives of others will only become evident in time. Will you save someone's life one day? What of your future children and how shall your experiences enhance their lives, and equally give substance to your own?
We all provide a vital purpose in some way and as bizarre as it sounds, your experiences make you question and find meaning to what many others completely miss.