If you are struggling with your payments then you should speak to the company helping you. They will be able to go through your income and expenditure with you and make a reduced offer of payment to your creditors. You may also want to consider the other options open to you such as bankruptcy or an IVA.
If you just stop making the payments to your DMP then your creditors will start hounding you again for payment and will probably commence legal action to try and retrieve the money you owe them. You should speak to your DM company or an insolvency practitioner however before you stop making the payments, they will be able to advise you (once they know all of your details) exactly what the likely course of action your creditors will take will be.