Stress really increases the symptoms of anxiety, and the combination of studying hard and trying to socialise is bound to be putting you under a lot of extra stress. You're at an important time in your life, so it's completely natural to be feeling under pressure, without having to deal with social anxiety too.
Your GP may be able to prescribe something to help as a temporary measure, but it would probably be worth getting extra counselling/therapy specifically to help you deal with this additional stress.