I would be pleased to answer your question.
The fact that your water filled lesions are raised makes the first possibility that of LeukocytoclasticVasculitis. This is a small vessel vasculitis
(inflammation of blood vessels in the skin) caused due to a variety of causes.
The second possibility would be of an autoimmune blistering condition known as Bullous Pemphigoid
. or Pemphigus Vulgaris
. In the stage before frank blistering the lesions can be flat and may appear bloody.
A third possibility would be senile purpura
, but here the lesions consist of flat bruises. This would have been the first possibility for you if you didn’t have a history of the lesions being raised.
I think you most definitely require a skin biopsy from one of the representative lesions. This should be sent for regular histopathology as well as for a test known as direct immunofluorescence (DIF). Your blood clotting profile and platelet count should also be done if not done already. These tests will help narrow down the diagnosis and appropriate therapy to be started. You should see a dermatologist
for the biopsy and blood work.
Hope this information is useful, please feel free to ask if you have any queries