Boyfriends childs mother/ Maintenance

Elle

Hi all, looking for some advice if anybody else has been through this. my boyfriend has 5 year old son with his ex partner. he pays her child maintenance every week. she also claims that he doesn't pay her so she receives social welfare from the government. his ex is hard to deal with, for example she won't allow my boyfriend to see his child today. she claims she doesn't get enough money from him. she holds him to ransom constantly by telling him the child needs shoes or clothes or toys etc. this has an effect on me also. as him giving her money all of the time means that I have to go without. I work fulltime and I'm 6 months pregnant with my first child. at the moment we have absolutely nothing bought for our baby.we are also trying to pay mortgage and bills. I don't want my boyfriend to keep up with her constant demands. I'm not sure if this is right. my boyfriend pays her a good sum of money every week but its never enough for her. she doesn't work and this pisses me off. I wud love to be able to be a stay at home mom but I cud never afford that. so I guess my question really is....what amount of maintenance should a man pay towards his child?? and when he's paying maintenance should he have to give more wen requested by the mother?? wen things come up? thanks in advance.