Hi Pinkpinot.
I get why you are pissed off. It isn't fair that he has access to ££££ pocket money while you are striking a watch battery and toothbrush off the list each month.
He might not like discussing finances and get defensive and argumentative, but tell him you want to sit down and go over the budget again. You need to make it clear that the disposable income left after bills are paid needs to be divided between you more fairly. It is unacceptable that he regularly goes out socialising and spending lots while you are unable to pay for new clothes for DS. Your DH has his priorities all wrong if he thinks that is fair.
I would tell your DH that instead of being given an allowance to cover bills, you would prefer the salary paid into a joint account so you have full access to money when you need it and can see all the incomings and outgoings. Then, you could both transfer a small (equal) amount of spending money to personal accounts to save or spend on whatever. The joint account covers all bills and stuff like grocery shopping, petrol and necessities for your child.
I would be furious with my DH if he begrudged me a few ££ for basic things for myself and the children, yet regularly lavished himself. Your DH is either a bit dumb if he can't see the unfairness of denying you more funds, or he is purposely financially abusing you. Either way, you have to challenge him on this and make it abundantly clear that he is mismanaging the money.
If you are unhappy with him and want to leave then seek advice from CAB or a family lawyer.
In the meantime, use the plastic for the clothes and shoes for DS and watch battery and toothbrush for you.