1 year ago I got dentures and now my jaws are sunk in & top lip is so small! Can this be fixed?

You may want to consider having bone grafts and then place implants to support your denture. The denture has to be made by a knowledgeable dentist or prosthodontist. 

Yes , but the size of the dentures, is strictly proportional to the amount of remaining bone, the height and width, this will make the dentures shape and size change. If the bone support its enough, then you can add as much material as you want,  also there are other solutions , like mini implants, with snap on dentures, also regular implants, and overdentures.

When you remove teeth the jaw bone starts to shrink and the denture does not support the facial tissues as well.  The best approach is to have a cosmetic denture made (not cheap)  Plumpers can be added as needed to fill out the face. Vertical dimension is critically important for a youthful look.  Cosmetic dentures can give you a virtual facelift in just a few visits.  Implants can maintain stability with a snap in denture and they help prevent future bone loss.

Usually it can be fixed.  Dental implants help preserve facial bone and lip support. A consultation with a board certified oral surgeon will help answer your questions.