Feeling the weight and dealing with white liars

I am oft-criticised for taking on other people's problems when I quite clearly have enough of my own. However, in a way, it is quite therapeutic for me. Basically, because I have such low self esteem and sense of negligible self worth, that when others confide in me the darkest parts of their mind I actually take some credit in the fact I am so trusted.

Strange, and slightly sad.

On the other side of this rusted coin, I also find myself too emotionally attached to people with problems, and begin to "care" too much. If there can be such a thing. This means that when they abuse my trust slightly, it hurts quite a lot. The worst type of abuse in this sense is the "white lie". The kind of lie that, on its own, isn't really very bad, but in the context of how much I hate them, very bad and effective indeed.

Basically, a friend has lied to me, about more than one thing, and the content of the lie is not the problem. I gave them the opportunity (more than once) to change their story, but they've chosen not to. Unfortunately, this person has told me many "white" lies before, and they all build up to a complete breakdown of trust.

I'll always be there for them, but I'll never truly believe the words they speak to me.