If you can't work because of sickness or disability, and you aren't getting Statutory Sick Pay, you might qualify for Employment and Support Allowance (ESA). There are two sorts of ESA – one is called contributory ESA and this depends on your national insurance contributions. The other is called income-related ESA and this depends on how much money you have coming in.
There are a number of tests you have to pass to get ESA. You can get help to claim this benefit.
For more information about ESA, see: Benefits for people who are sick or disabled.