I would highly recommend reading the book the Confidence Gap by Russ Harris. It's perfect for the kind of issues you're struggling with. It will help you get distance from thoughts like, "No girls will ever want me because I'm balding." Right now you're taking thoughts like that as gospel truth, when in reality it's just one of a million thoughts your mind is producing on a regular basis. It doesn't make it true because you think it. The key is to become an observer of these thoughts without getting fused to them. You notice the thought as just a thought and let it pass through your mind without getting caught up in it. Then you go back to being present in your life.
Imagine your brain has a window on the left side and right side. Right now, thoughts like that are entering your left window but your right window is closed, so you're stewing on these thoughts and they're causing you to spiral. These techniques will allow you to open the right window so the thought just passes through as it should without distressing you. It's a skill that takes daily practice, but it's very achievable.