Feeling weltschmerz, which I guess is feeling that the world and its material pleasures are ultimately not going to satisfy you, is a good thing. It hints towards the first noble truth that there is suffering.
However, focusing too much on it will make you sad and depressed, which is a negative emotion and not wholesome.
In Buddhism, there are various techniques to counter different types of unwholesome states of mind. When a car veers too much to the left, you nudge the steering wheel to the right. When a car is moving too slowly, you step on the accelerator pedal. But also the reverse is true with turning left or stepping on the brakes. Similarly, there are techniques in Buddhism to ensure that the mind stays wholesome and does not go into unwholesome states of mind.
Dhammadhatu's anapanasati (mindfulness of breathing) is one method.
However, being a young person, who should appreciate that both young and old people would not ultimately become and remain satisfied forever, from what the physical and material world offers, I suggest you to practise the Brahmavihara of metta, the meditation on loving kindness, whenever you feel the sadness of weltschmerz. It has many benefits.
Why do I suggest this? You should wish that all beings in this world, including yourself, should be happy at heart and and at ease. Yes, they may not be ultimately satisfied with what the world has to offer, but let them all be happy for this very moment and for as long as they can be. And this applies to you too.
From the Karaniya Metta Sutta:
Think: Happy, at rest,
may all beings be happy at heart.
Whatever beings there may be,
weak or strong, without exception,
long, large, middling, short,
subtle, blatant, seen & unseen,
near & far, born & seeking birth:
May all beings be happy at heart.
Let no one deceive another
or despise anyone anywhere,
or through anger or irritation
wish for another to suffer.
As a mother would risk her life
to protect her child, her only child,
even so should one cultivate a limitless heart
with regard to all beings.
With good will for the entire cosmos,
cultivate a limitless heart:
Above, below, & all around, unobstructed,
without enmity or hate.
Whether standing, walking,
sitting, or lying down,
as long as one is alert,
one should be resolved on this mindfulness.
This is called a sublime abiding
here & now.