On a property dispute such as you describe, you are going to have to hire a good real estate lawyer to figure out all the easements and encroachments. It doesn't sound like adverse possession (7 years to own) would apply, but there is no real way to tell without having the title checked, including all deed and plat records for the two properties, and the easement if it is a separate tract of land. Your ultimate fix is probably going to involve a surveyor, possibly your title insurance company if you purchased title insurance when you bought the property, and possible a court action to quiet title. And if the house is under construction and encroaching, you need to act before the house gets completed or a court may tell you that you waited too long to complain.
This answer is for general purposes only, and it does not create an attorney-client relationship.
The easement is limited to the purpose for which it was created. Ingress and egress does not mean able to build a structure. And yes, you need to deal with it now, or your right to recover your property will be lost to the statute of limitations. Malpractice on the part of the surveyor usually has a shorter statute of limitations - more like two years, so you may be out of luck on that.