Did you tell them you stutter? Sometimes self-advocacy helps and starting with that makes people more understanding. Maybe explaining what blocking is? Perhaps starting with approaching people individually? Cognitive Behavioral therapy might be beneficial as well. This article talks about how exposing yourself to social situations needs to be very gradual or it could make it worse. https://www.verywellmind.com/how-is-cbt-used-to-treat-sad-3024945