Sounds to me like a condition I get the first time I am exposed to the sun in the spring.
Man are they itchy !! They do get worse over a weeks time, sometimes enough to drive you crazy. I have had this condition for years, my doctor gives me a RX for hydrocortisone cream which takes the itch away and seems to minimize the size of the bumps. I also take an antihistimine as well. (Benedryl)
Doctor says reason for this is the pours in my skin fill up with fluid and its trapped under the skin, which tries to get out and can't....makes you itch.
I do hope you contact a doctor to see if your condition is as simple as mine.
It lasts about ten days.
Good Luck