As has (sort of) been indicated, you can't get a DBS check (at the relevant level) carried out on yourself. It has to be carried out (with your permission) by a potential employer (or voluntary organisation, as appropriate).
The only check you can get on yourself is a 'basic disclosure' but such a check only shows convictions which aren't 'spent':
https://www.gov.uk/request-copy-criminal-record
The two higher levels of DBS checks ('standard' and 'enhanced') are only available to relevant employers and voluntary organisations and can only be sought when the applicant is seeking work which is exempted from the provisions of the Rehabilitation of Offenders Act.
Both such levels show ALL criminal convictions (including those which are regarded as 'spent' for most other purposes). An 'enhanced' check (which is what is required to work in close contact with children) also shows any other information that the police might consider relevant.