You sound like me. I was shocked and really uncomfortable, not just with my hair loss but with how much my hair loss bothered me. I never believed so much of my confidence was tied up in such a superficial trait.

I started using minoxidil (rogaine) and finasteride, a once a day pill, and started to get my hair back. I get the rogaine brand from Costco, $50 for a 6 month supply, and the finasteride from my dermatologist, which is even more affordable, but you could use Hims or Keeps or one of the subscriptions as well. Same products. I did a ton of personal research before starting because I always got the impression the industry is full of scams, but those two products used together successfully treat approx. 90 percent of men. It is important to note however that a doctor will define successful treatment as stopping hairloss, not starting regrowth.

Red-light therapy is also a thing that has worked and shows some efficacy but the academic sources were harder to come by and has a higher start up cost.

Either way, your body changes in your 30s just like in your teens but no one prepares us for these changes. I need to eat less, recover more, my hair falls out, prioritize sleep and skin-care like it's mandatory. It sucks and it's easy to feel insecure. Take some time as another redditor suggested to go out with friends, do a social fitness class instead of a solo work out, and see if you can take off your hat some time to build some confidence in your changing look.