I'm Iron Man, And I'm Agent Coulson

So there is some sexy time stuff in here, but not alot, and sadly not overly graphic.
Synopsis: Apparently I have an obsession with Tony Stark, Agent Phil Coulson, and writing fanfic. So one night while watching Iron Man I decided that I would write a first person/Xreader that is with Tony throughout the first two Iron Man's, because she kida digs him. But the reader goes on her own way through Thor, The Avengers, Captain America The Winter Soldier, Avengers Age of Ultron, and Captain America Civil War. The reader won't be with Tony the whole time, there will be some instances where she will be with SHIELD and other characters from the movies.
The story will revolve around her and how she feels for Tony, and Phil Coulson. The Readers story then deals with her feelings for both men as she goes through each new movie.
People always say that you only have to fall in love once, that once you meet that person, it never really goes away, is Tony it for her, Coulson, or will someone else come along and steal her heart?