Pretty much. It actually means a group or a couple that share something in common. It's often made to be like... Relationship. Like in Naruto dojin, you get a lot of sasusaku and narusaku etc. which are fan art of the different pairs. So yes, it is often fan art, but it doesn't have to be a fan art. It can be just a manga about a group of people.
And btw... what you're doing would make you a dojinshika (manga fan artist).