I’m a Baal Tshuva, and for 3 years i've been wearing sefaradik Tefilin from the outer side ( either the Chasidish Busach or the ari's Nusach) eventhough I’m an ashkenazi, is this the correct thing to do? and if I want to aquire a new set of Tefilin what Nusach should I get, I don't have a religius familly background to follow. Thanks

The best will be to try to track your family origin, try speaking to great uncles or someone like that. Finding the place your family came from will give you a good guess of what is your custom is. If that information is not to be found – any Ashkenazi custom will be sufficient and Chassidic or Ar"i are perfect.