feeling a lil blue on new years eve

i examined my year and see it as more good than bad.  i am much better off than this time last year. 
i am angry with my ex b/c he is not paying support and is not even apologetic about it.  he is selfish and wants all the money to himself yet claims he does it for the children. 
im tired of having these discussions.  i blame myself for trusting him. i take the money out of our joint acct and he asked me to wait until noon.  i asked him y.  i thought it was to have some kind of control.  to take his cut first but i did not think he wld take it all.  that was my mistake. 
because thats exactly what he did.  he spent his whole paycheck in one day.  there was $8 left in the acct.
and his justification is simply that he had to pay his rent.  this is not the only missing payment during the month of december.  hes hardly given me anything.  he has consitently put the acct in the negative hundreds of dollars.
and we discussed it and of course it was fruitless
a wage withholding was sent to his job but hasnt kicked in yet
theyd bn sending it to the wrong place and it was not being forwarded; i did a little investigating and got the correct info.
then to add insult to injury his sister calls me to inform me that shes picking up one of my children for music lesson at her grandmothers house but the other children cant come.  my son cried.  and they leave me with a crying child. 
all the responsibility falls on me and they just keep muddying things
im stressed
trying not to be but i am
i think the next time im gonna say no
and then i wont have this stress