abuse questions for my nephew

My nephew is almost 3 and we feel he is being sexually abused.  My dad and his wife are staying with a man that abused me as a child.  He has been wetting the bed, playing "games" with the dolls, playing with himself until he is hard and won't stop, he has nightmares where he says he is scared of an ugly man, and he has also been playing with his "bottom" a lot.  I am most certainly concerned but we don't know how to ask him about it.  How do we find out who it is for sure?  I don't know what questions to ask to get an answer out of him.  We have asked where he has learned that game from (taking the dolls clothes off and getting on top of it) and he won't answer he just asks if he is going to get in trouble.  Of course we don't spank him or anything because we want to gain his trust for him to know that he can talk about it.  I don't want him growing up the way i did.  Please someone help me.  I need to know what to ask him.  Like certain words or how to phrase the question.

[koukla29]

I don't think you need to ask him anything.  He needs to be taken to a pediatrician so that he can be examined.  Explain what he is doing and ask that he be examined.  Pediatricians are obligated by law to report abuse, and you are obligated as his aunt to help him right now.  He is showing many signs of abuse.  You do not need a 3 year old to vocalize it - he is acting it out.  Please do something now because he needs you to help him.  Best of luck.  

[jo929]

it is to late with the questions you may do more damage than good grt him to a doctor now for his sake    lots luck     jo

[socgirl]

like the other posters said...he needs to be taken to his doctor for an examination.  At 3 yrs. old, he may not be able to verbalize what, if anything, happened.  Furthermore, if someone is abusing him, it's highly likely that the abuser would have threatened him or somehow manipulated him into not telling anyone and at 3 yrs. old, he may not have had the "good touch, bad touch" talk yet.  

Also, does your dad know he's living with the man that abused you as a child?  Have you spoken to him about this?  Does your nephew also live with your dad, his wife, and your abuser, or has regular contact with your abuser?  

Sorry you're going though this.