How to over come social anxiety

I’m not an awkward person in social settings but I have such bad social anxiety. You’d never know it when you see me but after I talk to someone I overthink the whole convo thinking about what I should have said, or did o say bye to quick and possibly cut them off, maybe they wanted to talk more and I just said okay have a nice day, maybe I said something stupid. Like I obsess for a long time which makes me dread small talk and social settings. My issue is mainly with small talk tho whether it be with the other parents when I drop my son off at school or a birthday party or when I have an appointment or whatever it may be. I never used to be this way at all. I’m not sure what’s going on or how I can overcome it because it’s driving me crazy.