7-14 days after missed period.
Clear blue digital.
Can, go to your preferred GP.
Best to do it on weekdays (Mon - wed) so you can get results faster. Alternatively, urine test at GP is immediate.
Up to you, if you get a negative and feel like maybe it’s too early, you can try again the following week.
Pregnancy may be one of the reasons for your missed period, other conditions like stress may also contribute to delayed period.
Good luck!