I can understand what you are feeling. Going to a new school is never easy. However, people do it all the time and it can be a great experience. In light of this, let me give you a few thoughts.
First, the way to make friends is not so much to think about yourself. To make friends, you ought to be a friend. As we do this, we find out one day that we have many friends. So, to the best of your ability, try to keep the focus off yourself and on others. The more you do this, the easier it becomes.
Second, you never know what the future holds. So, don't assume that it will be negative. Something great may happen with this change of school—new experiences, new opportunities, and even new friends.
Finally, just be yourself. If others don't accept you, especially as you try to be nice to them, they are the ones with the problem. In time, people will see this. If you are a loving person, the truth is always on your side.
Act naturally. There is simply no such large environment that cannot provide you with a friend.
Acting unlike yourself can often be tiring and will make you continually question yourself if what you are doing is right or wrong. The friends you will make when doing this will not be fit for you and you would feel worse than you would if you had no friends.
That is the only thing I can suggest. Acting like you do in a normal environment is the key to success. If you purposefully have an attitude that makes you reject all social interactions because you feel like you do not fit in a community, you won't fit it, but that is only because you are acting that way.
When you do find a friend, don't let the opportunity fail. Stay the same. Sure, this new school will have influences that will cause you to act differently, but those are long term effects of being in a new environment.
It sounds like you're going to a Catholic School. Good luck there!
Last but not least, worrying about whether you appear to be a loser to others is the least of your concerns in school. School is a place a learning, not only a place for socializing. Only care about yourself. Don't question what you think others think of you. Be confident of yourself and the way you act naturally.