I've always been like this. I just don't like asking for money for my work.

I've helped people on projects who have offered to pay me and insisted but I never take up their offer.

I've just got a new job and in the offer letter it says I can negotiate and "discuss further" my salary. In reality, I'm not happy with the salary at all.

But it's a new job and I don't want to seem like a troublemaker/difficult employee right from the beginning.

Any advice on how to alter this mindset so that I'm not cowardly when it comes to negotiating pay?

For context, I'm not weak like this in other aspects of my life. It's just money. Perhaps it's because I come from a poor background. I don't know.