Do I need to have a boyfriend/girlfriend
Is not having a relationship bad?

There is nothing bad about not being in a romantic relationship. You are a whole person; you do not need a significant other to complete you. You have so much to offer the world! Plus, singleness offers great opportunities to figure out who you are, develop good character, and pursue interests and activities you love. If you are interested in getting married some day, your single seasons allow you to focus more fully on cultivating in yourself the traits that will help you best love and serve your future spouse. When you are single, you have the freedom to make decisions about your time and future without having to consider a partner's schedule and needs. You can make impulsive (healthy!!) choices because you only have yourself to care for.
However, if you are asking whether it's bad to live a life void of any relationship, including friendships or intimate family relationships, then I would say yes - that is bad. I would be concerned if someone didn't have any loving, caring non-romantic relationships. As humans, the need for relationship is built into us; to deny that need is to starve your soul. Of course, you can't choose your family; I would be naïve to believe that everyone enjoys great relationships with their parents and siblings. Yet if you cannot point to anyone – within or outside of your family - whom you know and who knows you on some level, I would suggest that it's time to be proactive about finding some mentors and friends.
Stay awesome!
-Jaime