its such a cliche now-a-days, but seriously harden up and go to the doctor.
you are not wasting their time. its their job. they get paid to do it, by you and your taxes.
all you have to do is explain your situation, say you are concerned about every aspect of your life, you would lik to do blood tests and all that jazz, even get your wang out and get a jazz and pee sample on the go. poop in a cup too for stool samples.
just get it done man. doctors love having something to do that isnt just - here have some anti biotics.
£850 is a total con.