Voiding cystograms side effects?

I've just read a "thread" on another web site regarding pre-schooler's and masterbation (masturbation). I, too, have a 3 year old girl who frequently straddles our couch arm and squeezes her legs together. She is NOT humping. She said it "feels good" when asked what she is doing. I've been concerned about this behavior and it was a comfort to read that this is typical sexual discovery. I've raised two sons.......and I guess the whole sterotypical behavior of masterbation (masturbation) was easily accepted by me with them...because they were boys and "boys will be boys". Having a girl is "new to me" and I guess I was just not well versed that little girls also engage in this activity. I've not taken her to the doctor regarding this, because of the fear of a HUGE investigation and suspicion of child abuse would result. She never touches or rubs herself. I began to notice her "attention" to this area almost immediately after she was potty trained. We were at Wal-Mart and she pushed her "area" against the bars in the child carrier of the cart....then she began to push the leg divider of her car seat in toward her "area" while in the car. Now that I have her sit inside the cart while shopping and she is now in a booster car seat....she is just doing the squeezing the couch arm thing. She will now only do this behavior when NO ONE in around and we just kinda "catch her" in the act. She quickly stops and says, "I'm not doing nothing". This change in doing this behavior only in private is thankfully because I've explained to her that because this has to do with her "private parts" she needs to do this only in private. I'm trying to make this "OK" for her but it is a concern.

My daughter is extremly bright and is starting preschool this fall......so after reading some other posts on this subject I feel better and hope to see this behavior slowly decrease and terminate as she gets more stimulation from the outside world!!

Another thing......my daughter had to undergo a "voiding cystogram" because of kidney reflux at the age of one and again a few months before she turned three. Could this invasive diagnoistic test "awaken" her senses in this area. Ever since she had this test, she has always been very guarded of her urthea area when I would change diapers and after potty training during bath time. She has NO problem with me helping her wipe after peeing....just the thorough cleaning of that area.

Advice please............please help validate that her guarding may be due to her tests/UTIs and the masterbation (masturbation) OR whatever you want to call it..."self pleasing" is typical pre-school behavior.