Philosophy is what you need, my friend. Go on youtube and search for 'The school of life' channel. Specifically watch the philosophy series. Watch the perspectives of some of the greatest philosophers and let it sink into you. My understanding is that it will take a few months before your mindset has adapted to things you read/watch/hear/are influenced by.
I especially liked Camus point of view, which was something along the lines of: always rebel against what the situation forces upon you. So if the situation forces you to be sad, rebel against it, say that life won't force you that way. Unless you want to be sad ofc, then don't rebel against it. He told the story of sisyphus. The gods punished sisyphus for something bad he had done by forcing him to roll a boulder up against a hill. When on top of the hill, the boulder would always roll back down, forcing him to repeat the same thing over and over and over again. Naturally, you would think that this is absolutely pointless and made sisyphus sad. But he rebelled against it. He found the joy in the endless and pointless punishment, which rendered the task pointless to the gods. The gods wanted him to be sad, but he was actually happy. Now the gods were sad.
Do you understand the story? If not, this video (also the channel is great) might explain it better:
Watch the whole video.
Also existential
Wise or Not Wise is a great site. Some of them are really worth the read. Also, writing anything that comes to your mind (be it sad, happy, frustrating, angry, emotional, etc etc) to yourself can be helpfull. You can write anything, so don't limit yourself like you would do when talking to someone else because of shame, judgement or whatever.
You have to stop telling yourself things are pointless, becuase ultimately you can't be sure of that. IF they are pointless, then that means you don't have to worry about things being pointless, becuase EVERYTHING is, so you might as well enjoy your time here.
Hope you can do something with the above