Is my behavior indicative of a mental disorder?

I feel the same way some of the time, I like my solitude, but also feel lonely and want company sometimes. Perhaps not quite the same as how you describe, but I do think I can understand how you are feeling. I don't think it's a mental disorder, more just a minor problem which you need to think about and overcome. I think the problem is that you're possibly reading too much into things, have people mentioned a lot that you act cold towards them? Maybe you just think you're acting really cold, but other people don't see it that way. Talk to a close friend or a family member about it, perhaps in writing or on the phone if that's easier, you might find that you're not as bad as you think you are :)