how to deal with being the dark horse in a group of friends?

That, if true, is the most telling thing you have said.

I'll keep it simple:

Anybody that doesn't trust you, isn't worth keeping around usually. I say 'usually' because, sadly, sometimes we need people, for various reasons. Sometimes, they have a connection that could help us in terms of employment, in terms of meeting others, and so on and so forth. But each of these should be weighed very carefully, because they are not always worth shady or untrue companionship.

If you have made efforts to be their friend, and to gain their trust, but they do nothing, then as hard as it may be, it is to be considered, that you leave them alone and move on. Unless you give and receive back trust, a relationship will never grow or, worse, it will die.

 

Honestly if it was me I would dump them and find some better friends love yourself and know what you deserve. If people treat you less than you deserve then they are not worth your time.