Hi, I'd like to help you with your question.
I believe you are right, your feelings of insecurity probably go back to childhood or young adulthood with something you went through. A poor relationship with your parents, peers, siblings or even a few off comments by a stranger can sometimes stick with us and make us question ourselves. It becomes a learned behavior and we need to learn another way to think about ourselves.
What you can do about it is start to work on your thinking. That is where the insecurity is coming from- your thoughts about yourself. As you said, you are attractive, intelligent and have a pleasant personality. Those are all great traits. So it is your thoughts about yourself that is causing you to feel this way.
Start by thinking about situations in which you feel insecure. Identify your feelings about these situations. For example, you have trouble when talking to other people about yourself. Identify how this makes you feel. Do you tell yourself that you are not good enough to talk to them?
Once you get an idea of how you feel when confronted with these situations, begin to challenge what you are telling yourself. Why would I think I am less than these people? There is no reason for that feeling, for example.
Begin replacing the negative thoughts with positive ones. For example, I am just as worthy as anyone else. Go through all of the thoughts and self criticisms and challenge all of them.
Forgive yourself and allow yourself to be human. Be kind to yourself and realize everyone makes mistakes. Give yourself permission to be you, in any situation. If you start by being nice to yourself, it becomes easier to accept yourself in all situations.
If you find that you have trouble working on this issue by yourself, see a therapist.You can ask your doctor for a referral or try on line at www.find-a-therapist.com
I hope this has helped you,