If you have an HMRC Self Assessment account it actually has a function where you can check your NI contributions to see if you are short or not.
As annoying as the 'contracted out' thing is it will really only affect you if you want to retire early. If you are able to retire early then you probably don't care about state pension.
For most people who start working at 18 and retire in your 60s you will still have a full state pension. For some of us it won't kick in until we're 68 though.
BV