I messed up

Last night Gman was taking a bath and I had my feet in the tub with him.  As I was getting them out to get a towel to get him out, he started to try and pinch me with a pair of plastic pliers that he plays with in the tub.  I said “Now why would you want to do that?” and his response broke my heart.  He said, “Because I am an evil, evil boy.”  Seriously, even just thinking about it makes me want to cry.  I immediately stopped what I was doing and got up as close to him as I could and asked him if anyone had told him that.  He wouldn’t make eye contact, but I persisted and he ended up saying he was just joking.  I don’t buy it.  I think my bad attitude has affected him.  I think I yell WAY too much and tell him that he’s being a bad boy or mean and I think he has internalized it.  I think I am a horrible mother.  No wonder God has answered my prayers for another child with a resounding NO.  I’m screwing up the one I have so bad that it would be injustice to send me a second one.  The other day he said he was a “mean boy” and I corrected him, but obviously I’m doing it wrong and making him think there is something wrong or bad with him.  He’s only 3 [going on 4], he shouldn’t think he’s bad.  He is a boy and he is a 3 year old boy.  He’s mischievous and a bit rough [okay, a lot rough].  He doesn’t understand why it isn’t funny to hurt people.  This morning while we were saying our prayers I made sure to thank God for my wonderful son and say how blessed I was to have him and how wonderful I think he is and how good.  How can I teach him to be kind?  How can I teach him to be the wonderful little boy I know he can be without making him feel bad about himself.  Oh God, please help me to be the mother you want me to be, help me to lead my son to love Your Son and to be the man you want him to be.  I am feeling so lost and horrible and helpless.  Please God, help me.