Do not want to marry girlfriend but have committed to the marriage

Hi,
It seems to me that you are extremely self aware of your feelings and the role you play in this situation. You know the exact consequence of each of your actions and how it will affect others.
You seem like a person who really cares a lot for your girlfriend and the others around you.
However marriage is a decision that needs to be taken after thinking about it carefully.
It's a decision that is taken by two people who are consenting to it.
If one partner does not want it and is unhappy about it, it directly affects the happiness of the other partner.
You and your family are scared of what people might say right now for calling off the wedding but it is still a better decision than getting a divorce years later.
In the end of the day, regardless of what people say, you're the one who has to be married to her, not them.
That being said, be prepared for dealing with the consequences of calling of the wedding. People may talk and say hurtful things about you, but it's important to be strong and do the right thing for yourself as well.
In the long run, you will have protected your partner from any further pain and shame.
Have strength and stand by your decision.
Hopefully one day, your partner and your family will come to understand you.
Take care and all the best to you.