Sorry if this has already been mentioned but you need to talk to your accountant about which classes of National Insurance you've been paying. You need a certain amount of Qualifying Years over your lifetime to get the State Pension. Unless anything has changed, a Qualifying Year is one where NI was paid for all 52 weeks of the financial year. Your Child Benefit will count for this from now on, but the amount of Qualifying Years you need for a full State Pension is more than 18. So you need to have paid some Qualifying Years out of your employment years when you didn't have the Child Benefit.
Employees: full time will have been paying NI from their wages, part time it depends how much you earned per week whether you paid it or not. So you could have some Qualifying Years from this.
Self employed compulsory NI is Class 1 but this doesn't qualify you for State Pension, you need to be paying additional Class 3 NI contributions for that.
If you need/want to, you used to be able to backdate your NI contributions for upto 5 years, check with HMRC if this is still the case if you're interested. Backdated NI contributions means you pay them as a lump sum to HMRC so you can get those years as Qualifying Years towards State Pension. Whether you need/want to do this depends on how old you are and whether you have enough years left to pay NI during or receive Child Benefit during before you retire.
You can get a Pension Forecast from somewhere so you can see how many Qualifying Years you've already got and whether, with your current working circumstances, you're on track for a full State Pension or not.
FYI, NI isn't only for State Pension it pays towards all the stuff society needs schools, NHS, welfare benefits etc that's why working people pay it. Having NI contributions also qualifies you for other benefits sometimes, that's why there's contribution-related benefits and income-related benefits, if you fall on hard times there's two chances to qualify.