I don't have any clear memories but I'm pretty convinced that if anyone had asked me directly I would have denied what my father was doing to me.

A few reasons why:
Abusers groom their targets so that feel feel they are responsible at least in part for the abuse.
Abusers tell their targets that no one will believe them
Abusers tell their targets that they will be responsible if they tell and the family falls apart or their abuser gets sent to jail
Abusers make their targets think it is love
Abusers emotionally isolate their targets from anyone else so they do not trust anyone else
Abusers threaten their targets with physical violence against them or their loved ones if they ever tell

My father used all of these tactics.
A young child is not able to see through these lies, s/he does not have the mental capacity to do anything other than accept the adult's word.

If your daughter is being abused she will need very gentle handling and be shown tonnes of reassurance before she will admit to anything. She will not do that unless she feels safe. Because you are emotionally involved it will be extremely difficult for you to do this so I suggest you talk to a child support agency or a therapist and discuss the best way forward. There is also the danger that if she discloses to you, the abuser will say you incited her to say it through sour grapes or whatever.

Thanks you for listening to your daughter, for listening to her body language and daring to see what might be causing it. You are a strongmama.

Seconding breaking's excellent advice...you need pro help.

Listen to your gut. Investigate further.
Take notes of things (with date and time) that raise your suspicions.

This list of signs seems fairly good:
http://www.rainn.org/get-information/types-of-sexual-assault/child-sexual-abuse

Personality changes would be a big one to look for-an outgoing child becomes painfully shy, or a mellow child becomes angry and lashes out.
...A huge clue would be if they are reluctant to be left alone with any specific person.

I always denied it whether questioned by teachers or grilled by those doctors due to fear. Fear that I would "pay" and fear that they would be hurt also.
The other replies are awesome and I stress the change that happens as quickly as overnight. The withdrawal, shutting down, a look of deep sadness and despair, as well as acting out, anger etc. Most of all those windows to the soul, the eyes, never lie. I call that look "dead eyes", yet they may look filled with pain and/or look like they're far away, a look of "lost".
I hunted around and came across this, www.rainn.org/get-information/types-of-sexual-assault/child-sexual-abuse/if-you-suspect Hope this helps, Blaine

I really appreciate you all sharing your insight. I am working with a therapist who actually took my concerns with a grain of salt until she actually met their father and it felt weird to her. She actually called me and said that red flags went up and she wanted to investigate my concerns further. She's trying to establish a good relationship with the girls so that they feel safe.
Today, I caught my girls in a sexual type of act! They are YOUNG and I only allow them to watch Disney Jr. and stuff. The other channels are locked. THey would not disclose where they learned that.
I know you all have been there - -but I've been trying to get help for YEARS. YEARS. i'll never forget Child Protective Services and how the police officer never even questioned their dad in person. She called him. he denied it and that was the end of it.
Dismissed Dismissed Dismissed everywhere I turn! I am so grateful for this one therapist who actually doesn't think I'm crazy

How do I protect them when they have to go to his house twice a month? I reinforce all the time what is appropriate. I've even thought about moving away - which kind of sounds crazy, right?

yes yes yes. my only mission was to stay in denial and never let anyone know my shame or guilt. Follow you gut it is ussally right. Becoming defensive is many times a reaction that is considered a flag by professionals. When i was working with abused kids i looked for reactions like becoming defensive.

In my past life of working with young kids, as young as eight, I found the direct approach was very limiting in breaking thru a childs fear and believe me it is fear that holds them back.

I always took the indirect approach and it work well most of the time.
Each child is different and so should the approach.

if you would like to email feel free. I can share an experience or two where i was able to get kids to open up. what is important is not put ideas in their minds. Kids who have been abused can latch on to any idea that they feel can protect them from the real truth you are trying to get to.

justanothersurvivror.wordpress.com

good luck

rich

I don't remember being asked. I was kept very close to my parents. My mom even started working at the school that I was in. I couldn't escape from them. Of course, dad didn't allow me to date or even talk about boys. I would have denied.

Breakingtheshell: Your list of reasons were amazingly close to what I was told. It brought back some memories....which was a good thing now that I can manage them better.......Zoloft....

I denied it to my mother the only time she asked because my father made the money, and he told me that without him making the money for us to live on that my mother and I would die. I believed him, so I kept my mouth shut. Kids will deny if they think anything bad will happen if they disclose. My mom and I had a decent relationship at the time too. It's very hard for a kid to disclose. When I was in High school, my parents told me they were getting divorced and my father told me he'd get sole custody of me. I was so scared I became suicidal and started cutting myself to relieve some of the stress. Go with your gut. If you think something bad's happening, it probably is. Is there any way he can get supervised visits? atleast then you'd have a little more piece of mind knowing your babies are safe.