You may get Jerome K Jerome syndrome ! In Three Men in a Boat, he decides to take a boating holiday because he has been reading a medical encyclopedia, and has discovered, to his alarm, that he has symptoms of every disease and complaint in it. Medical students, he mused, could be brought to see him, who had everything,and so not have to study dozens of cases. He hadn't, I think, got 'housemaid's knee', and soon felt indignant, rather than relieved, that he hadn't.
Surely, googling symptoms is likely to produce false diagnosis because an anxious person will imagine that they have symptoms they haven't, or have only slightly,thus completing the picture of all symptoms for the illness, and in any case have not the medical knowledge to interpret symptoms, rate them in significance, or rate the likelihood of their having any particular illness or condition.
I have never self-diagnosed. I don't buy a guard dog and then bark myself. One of us is trained and equipped to do the job. I'm not. That's why we have doctors.