I'm the same way, and it's not antisocial behaviour at all to need some time to yourself. You may simply be introverted, which means that spending time with people is what uses your energy and then time alone is what recharges it. It seems most of the world is the opposite (gain energy by being around people) and don't understand us introverts. A good book on the subject that might interest you is "Quiet: The Power of Introverts in a World That Can't Stop Talking" by Susan Cain. I learned about it first on her TEDTalk about introversion.
The fact that you are shamed for it clearly means they don't have an understanding of your needs. Perhaps they should be reading that book!
Hang in there, Aurielle. I totally understand how that kind of situation can make you feel more alone than you wanted to be. You just need some time and space to recharge your batteries!
Of course the other possibility here is that you are experiencing some kind of social anxiety. If you feel anxious or frozen in a way when you're around people, I would recommend reading up on social anxiety. You can find all kinds of tips for coping with this on Google.
Sorry for the long response. To answer your question briefly, these are not the signs of being antisocial. People misuse the term often, but it actually means "contrary to the laws and customs of society" - wanting to be alone doesn't contradict any social laws or conventions.
