Please help me

I(24M) have been extremely stressed in the past one year after I moved to US. I am thinking way too much and it's messing with my perception of time and smell. I don't feel like doing anything and I am unable to understand anything. I am in grad school and these things are taking a toll on my life. I feel terrible from the inside. I usually would enjoy sports and TV shows but I am unable to understand what is going on while it watch them. I tried multiple types of antidepressants for a year but they don't seem to work. I've started stammering severely. I make pathetic decisions which cause me trouble. I don't know what to do. Please help me and guide me.