Ant-Man release date?

Okay so not sure if it's just me,but shouldn't Ant-Man be released before Avengers:Age Of Ultron.I mean come on Marvel the whole backstory of Ultron is based off of Hank Pym's(Ant-Man) experimenting with A.I and failing therefore creating Ultron.So I ask the public this shouldn't Ant-Man come before Avengers:Age Of Ultron?I understand the Avengers came first,but how can you have a villain with literally no backstory,Loki had Thor,and You know who had Guardians Of The Galaxy, Deadpool, Sabretooth had William Stryker,and Wolverine,and Winter Soldier had Captain America.So why can't Ultron have his creator?Not saying this will hold me back from seeing the new Avengers:Age Of Ultron being released May 2015,but it would be nice to have some explanation as to why this is so.When Marvel has never had a villain without a reason he has come to be.