Do you have to be diagnosed with social anxiety by like a dr or therapist?

I’ve always been the quietest person around strangers. The dream student & worker because I keep to myself & just work, but now it’s starting to affect my relationship... my SO works every day occasionally has Fridays off. Today he wanted to go play pool with his friends & their wives.. convinced me into going, we were there for 15 minutes & I was dying inside I felt trapped so I texted him I wanted to leave.. I’m now waiting at his mothers house while he continues his fun w his friends... I hate it so much but it has a strong hold on my life, I just don’t know who I need to see about it? We’ve been together 10 years & im sure he knows I get anxious but I don’t think he knows the severity of it & it’s also not something I like to admit to..