I Have Small Pimple Like Red Spots - They Itch

i have small pimple like red spots - they itch just a tiny bit - they form scabs - when take the scab off - there is depth inside. They are perfectly round - sometimes they form a small line. They were on my ears, by my eyebrows - but mainly on my legs - by ankles. The Dr.s dont know what it is - one said flea bits - but my dogs don`t have fleas - I had them checked. I Derm. said it is an infection - put me on antibiotics for a month - didnt do anything. They are so strange - have had them for a year - they have gotten worse in the last 2 months. I am not allergic to anything. I am in my fifties. When the scab is off - you can put your finger inside and feel a perfectly round indentation - it is so strange. Another Dr. said it is like eckzema.??? I really would like to know what they are. They fade - but after months - you can still see a slight red round mark where they were. I just want to know what they are? Thanks-
Lori