Child support

Hey just a quick question, me and my son dad ain’t together as such. He comes around twice a week and sleeps over 1 night a week. He offered to help and pay me some money each month but I said it’s ok as i was just glad he was apart of my son life (was around the full pregnancy). Anyways he buys the odd things like he just brought him a high chair and if I need anything like nappies I can ask him and he will get them. However I’m really starting to struggle on maternity pay and my bills just keep going up and up. Am o wrong to ask him for abit of help ? And how do I ask him . When he comes over on the weekend I’m also buying the food or take away for us both. I worked out last month he would have spent about £60 on him and he got a really good paid job and I know he wasting money on a certain “thing”