GPs and testing labs are run off their feet without testing everybody for "faulty platelets", especially as the "fault" isn't properly understood.
It's known which groups are at highest risk without testing everybody individually. It sounds as though you're at high risk for a number of reasons. No amount of testing is going to change that.
Sadly, unless community transmission, including amongst children, is reduced, you're going to have to take maximum precautions.
Approximately 1 in 200 people is currently infected. Hopefully, most of those people are at home isolating, but there will be others who are newly infected and are asymptomatic. That means in a busy supermarket, there is likely to be at least one infected person at any time. Children and people in their 30s are more likely to be infected, so you need to stay away from them and their contacts. Apart from avoiding enclosed and crowded spaces for more than a few minutes and wearing a mask, there's not much more you can do.