Thank you for asking us to respond to your concerns. There are several things that come to mind as to why this may be happening, but I think the more efficient thing to is to approach this in a functional way.
You are feeling a lack of self-confidence, and because of this your self-esteem has taken a hit. I suggest three things to help bring about a change.
First, I would find an individual therapist who is also proficient in group therapy through the counseling center provided by your college. I believe talking to a therapist one-on-one is a good beginning, but ultimately finding your voice within a group will be very helpful. The rich dynamics of group therapy will allow you to feel the inhibition, but in the safe environment designed for experimentation. If you can’t find someone with both, begin with individual therapy and ask the therapist or the counseling center about helping you find a group to join.
Secondly, I would get a medical evaluation from a psychiatrist. What you are describing is emblematic of several issues that may be helped directly with medicine. An evaluation would determine if there is a remedy available.
Finally, I would take an introductory acting class. I know this may sound unorthodox, but I have been recommending this for many years and people are astounded by the progress they make. Engaging in acting exercises and scenes with fellow students is an easy and fun way to confront your fears.
There may be other issues or concerns that emerge from your therapy, but I believe the combination of group work, medicine and finding your voice in an acting class will be a good way to begin.
Wishing you patience and peace,