With this little information, it is difficult and would be wrong to label you with a psychological illness tag. Hatred for festival and people enjoying festivals must come from some past experiences. One needs to look at those closely to understand the cause and by exploring this, you will find a way to tackle the problem as well. A good therapist can help you do so.
Everyone has likes and dislikes, at some phase of life these likes and dislikes become stronger and create problem for us. You seem to be going through that phase now, please get in touch with a good therapist locally.
In general, watch your food and fluid intake, avoid alcohol and indulge in regular exercise. This will help you.