Being 18, starting college, is a huge transition and I totally understand the feeling of being overwhelmed and hopelessness. The avoidances...not speaking in class, at work are all reinforcing the fear of stuttering. It will be in baby steps but try avoiding less. Going outside your comfort zone is key and it will decrease your fear and anxiety. Fluency can be a byproduct of this. Give yourself a support group. Try finding a local stuttering group in person or online. You are not alone. Eventually learning to accept your stuttering can make things easier and help confront these fears and anxieties you are experiencing. I sense a lot of catastrophizing going on in terms of prediciting how your friends and others may think. You may feel this way, but in reality its probably not as bad as you think it is. We all have bad interactions and we dwell on those. And thats how the fear digs deeper into us. Fear makes us predict the future and makes us assume a bad reaction is going to happen every single time. You are young, the world is your oyster. I wasted my college years being paralyzed by fear. Dont be me. Take chances! The worst that can happen is you will be in the same place. And thats worst case scenario. You will find a way to get through this.