How to be more secure in myself?

Yes, I understand exactly what you're going through. It's very hard to over come, but you can get rid of it. Like Michael said, it takes time. You need to learn to trust, even if it means one person at a time. Once you are able to trust one person, you will beable to go on and trust more. Soon your paranoia will be mostly gone. Being confident in how you look, your intelligence, and your capabilities is a great start. Now you just have to learn to trust them and yourself and soon you can trust others. Don't worry about the things that are not, even if you think that people are doing that to you. You're wasting your life time worrying where you could be thinking of a bright future if you dont have yours already and be happy that you are who you are. Knowing that will give you the conclusion that people do like you, and dont say anything behind your back.