I am having social anxiety

I have anxiety for so many years , after i got admission in my junior college i started to have social anxiety too and now I am in University , studying for my under graduation and have been facing extreme social anxiety . I have not attended my classes nearly from three or four weeks now it's getting me a headache when I think if I avoid my classes every day like this what will happen of me . I hesitate to speak in front of large groups like in my class and when I think if I go to my class what will be the profs reaction and they will ask questions to me and I don't have courage to speak in front of my classmates and my classmates will make fun of me . Some of my classmates saw me roaming here and there alone at the time of my lectures , wasting my time , they will think I am mad but really I am not able to face any of them . I can't share it to my parents and any relatives but here . All my situations don't make sense but really I am very very much anxious and depressed about this .