Who would i talk to about my 33 year old EX sleeping with a 17 year old girl in oregon.?

Ok i have been dealing with my ex for some time now. well long story short. he gets my girls on the weekends and his roommates moved out and left there little sister there which was 16 when they all meet and moved in together but at the time the 16 year old wasent always staying there only on the weekends.well now that her brother and his wife have moved out because of complications with my ex. she has decided to move in completely with him.i found out acouple months ago they where sleeping together and she was only 17 at the time and it had been going on for atleast acouple months. well my kids have to see this so i called and reported them to several different people in the sherrifs department in marion county and to the crimes detective. well so for its been months since i talkedto them and the only thing that has been done is the detective went to there house when they werent there and left a card to have then call him. they dont plan on returning his call ever and nothing else has been done.he is 15 years older then her and it started before she turned 18 which was acouple weeks ago. does any one know who i can talk to that would take me seriuosly.