My 4 year old son has an xtra tooth, It is up the top next to one of the two very fromnt ones.

Is this bad and will it cause any problems with his adult teeth when it comes to that time?

He might need braces because the extra tooth might push all his other teeth forward. I would recommend taking him to the dentist.

I took him to the dentist about 2 months ago, I told her about the extra tooth but she didn't say anything or wasn't very concerned about it.
Im starting to wonder whether she even heard me say it or not.

An extra baby tooth is not cause any more problems then any other baby tooth. When the perm. Tooth starts to come in, it will push the baby teeth out, along with the extra baby tooth. I would keep an eye on it, just to be on the safe side. I hope this helps.