The reason why I hardly go out with my friends isn't because I'm antisocial.
Why don't you go out with them, then?
Sometimes if you go out too much, you become numb.
Friends are expected to spend time with another but sometimes its okay to take time for yourself and be alone. Just be sure to let your friends know the reason why you don't want to spend time with them or they might think they're the problem.
Fine.
Honesty is the best policy. Let your friends know when you need time to recharge yourself and be alone, it's okay to do.