Sounds like either COVID or an enormously long list of alternative upper respiratory viral infections. Just because your mom tested negative doesn't mean you don't have COVID as well.
Do I have some sort of respiratory infection22M, 5 ft 20, 235lbs. 2 weekends ago went to a family party and we were all drinking and started sharing a bottle that was passed around between like 5 people. The next morning I had a sore throat and just thought it was nothing. It continued for a few more days and after the sore throat went away I got really congested and got a really bad cough that I still have to this day almost 10 days later. My mom also had the same symptoms plus her sinuses were bothering her so she got a covid test that came back negative. I just assumed I wouldnt have covid if my mom didnt if we were both sick. The doctor at the clinic she went to said she had a sinus infection. I havent seen a doc yet but my sinuses havent been bothering me at all just my chest snd a cough. The cough is the worst in the morning then kind of slows down a little then picks up again around the time I want to go to bed. I get in nasty coughing fits to the point where I can barely even breathe and I cough up a ton of green phlegm. Ive had an upper respiratory infection before but it was never this bad. Ive barely been getting any sleep because of this cough. Ive taken mucinex dm, robutussin, and dozens of cough drops but nothing is working.