I've had a shadow above nose since I was 17. Does it have to do with my nose shape? (photos)

hello thank you for your question and provided information as well.. based in your question its difficult evaluate you if the case with this angles of the  picture, my recommendation is get  a consultation in person with a plastic surgeon to discuss all about theme

Based on the photos you've included, it looks as if there may be a depression in the radix - which is the starting point of the nose between the eyes.  Sometimes a relative depression in that spot can be noticeable in certain lighting specifically if it is coming at an angle or from above.  
Several things can be done to alter the shadowing effect including rhinoplasty to alter the shape of the nose and augment the radix or many surgeons are placing filler into that region for a temporary fix.  It is important to be careful with fillers in that region as they can damage the skin and get into blood vessels which can create serious problems.  If you choose to do anything about it make sure you see someone who is comfortable with rhinoplasty or those types of injections and performs them frequently.

the shadow at the root of your nose, also known as the radix, is because that area is deeper  than would be considered normal and your supraorbital ridge is slightly more prominent.  These 2 characteristics create the shadowing that is occurring.  This is a relatively straightforward correction with augmentation of the radix.  Augmentation can be accomplished with injectable fillers such as hyaluronic acid or hydroxyapatite known as Juvéderm and Restylene or Radiesse respectively.  These are any simple solution with the only problem being that are temporary nature and will last for only 12-18 months.  More permanent augmentation can be accomplished with the soft tissue or cartilage graft that could be placed surgically.