running out of options

i'm 26 yrs old and i have a 9 year old son. his father and i got together when i was 13 and he was 15 and we stayed together for 5 years. we have the most gorgeous son, but lately riley (our son) has been going thru something and acting out. riley goes to his dads house every weekend, and his dad and i had a great parental relationship. Then riley started acting out. his behaviour is getting out of control and i am constantly in contact with his dad to try and figure out what we can do to help him, but instead of helping, my ex just attacks me. his answer was to spank my son and i refuse to do it. my ex's response was 'no wonder he has no respect for u.' i personally dont think that violence is the answer. i believe his father and i should come to a mutual agreement as to how to handle the situation. he says i'm a sook. is it too much to ask for a little support? if i'm in the wrong, please tell me. and any advice would be much appreciated