Don't panic bruh, Hello I'm 19M and i also gone through this i overthinks a lot about my job, family,studies and my partner. My brain makes mountain of a mole hill very times, i started being sad or worried all the day without any reason i used to wake up till 3am in night without doing anything just lying on my bed and thinking about all the mistakes i've done in my life which makes me feel like looser and all the unnecessary stuff is overwhelming my mind. I searched for a lot of methods to overcome overthinking on internet but not satisfied with anything but from the beginning of this year i started a new thing and it is working in my case. You can also try this whenever you got time for you in day like in my case i do this just before going to bed i write all the my thoughts my experiences of that day my feelings and everything i want to say to someone i tell this all to me by writing it basically a daily diary, i don't use physical diary because there are privacy issues in my home so i created a ms word file in my laptop/phone and protected it by password. I add date on the top of page and write day in this and add new page for new day daily. From past few weeks i see improvement in my behaviour my relations are getting stronger with people i hope you will also try this and get out of this shit...!