One practical thing you can do is to see if you can improve the situation by experimenting with your diet. Specifically during the hours before you sing, but also in general. The throat and sinuses can react differently based on what you are eating, and what your blood sugar is like and so on.
For example, if you use a lot of caffeine, you might find that reduced caffeine or no caffeine improves things significantly. If you smoke tobacco, then not smoking might help significantly. You might try less sugar, especially right before you sing. All of these things are stimulants, and so is the nervousness you feel before singing, so you can end up essentially overdosing on stimulants before you sing. The nervousness simply pushes you over the top. If you arrive at the microphone a little lower, the nervousness may push you up into a good zone for singing effectively.
Another typical thing to look at is dairy. It will increase the amount of mucous in your throat and can make your throat react differently than otherwise. Many singers give up dairy at least for 4–8 hours before singing if not altogether.
From my own experience, when I embraced a diet that is rich in micronutrients — eating lots of raw fruits and vegetables, lots of salads — for some reason it really opened up my throat and sinuses, as though I had taken a giant hit of menthol, except healthier and the feeling lasts all day, everyday. It dramatically improved my singing experience. Not so much the way I sound, but the way I feel when I’m singing. Light instead of heavy, open instead of closed. I don’t get distracted by my physicality while I’m singing. And I get fewer colds. I have more “peak voice” days.
Of course, make sure to be fully hydrated. Sipping water regularly is obvious. Another thing that is really great is fruit and vegetable smoothies made with a NutriBullet or similar device. They are very hydrating because they’re like time-release water. You drink one and your body continues to gain hydration for some time afterwards. And it is a light meal to have before singing, which can also be beneficial to the way you feel at the microphone. During the hours before a recording session or show, fruit and vegetable smoothies is all I will eat because then I find my throat is hydrated and comfortable at the start of the session and I’m not constantly reaching for water, and yet also not running to the restroom all the time because I’ve been pounding the water. If you arrive at a session or show already dehydrated, it’s basically impossible to catch up during the session. You have to maintain good hydration and nutrition when you’re not singing so that it’s there when you sing.
It is actually very common for people to have what they think is a psychological problem and then they cure that problem with significantly better nutrition. Even things like severe depression or severe anxiety disorders. It is worth a try because there really isn’t any downside to trying. Even though healthy food can be more expensive and more time-consuming, it is still cheaper and easier than the typical psychiatrist, and much cheaper than the opportunity cost of not singing because of health problems.