My selfish behaviour has caused a lot of trouble.?

For a while I've been almost certain that my mother wasn't sexually abused as a child. She has talked about it often happening when she was 4-6 years old so memory is usually foggy around that time of your life. I've studied psychology and I was adamant that the psychologists she has visited were planting these thoughts in her head or, rather, over-encouraging her own thoughts about it. Sometimes when people hear something over and over again they begin to imagine it really happened rather than simply a dream or something they watched on television that can somehow make themselves believe it really happened to them.

Anyway, I went to my grandmother and asked her very vague quetsions aobut why my mother is messy (something that is almost intolerable to live with and I'm going crazy) I probed into where she stayed when she was younger - I never suggested sexual abuse - but my grandmother said that she was the only one that ever looked after her and she said it very strongly.

So I was so sure that my mother devised this in her head and I told her what my grandmother said, she got really offended as in the past I told her that what she might be retelling may not be the truth (I never said they didn't happen.. just that they might not have happened). This time I said they can't have happened.

Anyway she went to my grandma and asked her... well did she have something different to say! She told my mum, yes, she was baby sit by a family with a boy and also baby sat in a boarding house with a man. On both accounts they were both exploited for their sexual advances. (They made my mum touch their privates and also pull my mums pants down. I dont think they did anything else though).

I'm stupid, naive and ignorant. The day before new years day... and confirm my mums suspicians... and my grandma? If she has a heart attack its my focking fault. I don't know what to do/feel :( Just feel like apologising over and over but I don't think that'll make a difference