Someone who is a combo of a liar, an exaggerater, and have a tendency to construct stories [duplicate]
mythomaniac
mythomania (Psychiatry) the tendency to lie, exaggerate, or relate incredible imaginary adventures as if they had really happened, occurring in some mental disorders
http://www.thefreedictionary.com/mythomaniac
As @ermanen points out, the one-word that matches your description would be :
Mythomane , noun, meaning- a person with a strong or irresistible propensity for fantasizing, lying, or exaggerating.