Boyfriend, baby mama, bills...

He has 2 girls different mothers & i have a daughter & a son same guy. I don't receive child support so I pretty much handle what I can & cannot spend to be able to provide for mine. My boyfriend pays child support automatically gets taken out every week. We recently decided to live together about to be a month from our move in date. 

We've came to an agreement to cut down on something's that aren't necessary to be paying off for example his rims & tires (superb expensive payments) to be able to live comfortably. he doesn't provide for mine...but he does have to pay something of the household...he tells me his 2nd mother of his child has been asking for more $ on the side saying they're daughter is getting older so she's struggling idk anything about her idk the type of person she is or if she works or she goes to school. What I do know the daughter is 1 & she's breastfed so I know for sure no money is going towards formula, milk etc. I honestly don't agree for him to be giving her money on the side when we decided to have a little extra money from dropping the rims & tires so it can go towards nthe household not personal needs....idk how to bring up the subject to him that I don't agree to give the mother more money a week for things that don't add up. & I don't want him to feel that I'm against for providing for his daughter when I'm a mother myself of course I want her to have everything she needs just don't think the amount they have court order don't see how it isn't enough any suggestions?