This is just a thought and of course a doctor would have to diagnose you, but I have had those pairs of red pimples on my chest with a bit of a painful and sensitive sensation (clothing even bothered it to touch). I've also had them on my leg with there was a pattern of skin sensitivity that went along with it; lasted for around 10 days or so. When speaking to my doctor, at a time when it wasn't "active," he said that it could have been a light case of shingles. The pain and sensitivity always kind of made a path or pattern in a circular way, like spiraling around my leg, and earlier, around my chest and back.
I have the same thing. It started on my chest ( i thought they were pimples ). Then i got them on the back of my leg, nape of my neck, back of arms. I went to the dermatologist and he told me that it is infected hair follicles. My best advice would be not to pick at them or try and pop them because it will make it worse and you will scar.
It can be due to pityriasis rosea, viral infection, allergic reaction. Pityriasis rosea is a common human skin disease which presents as numerous patches of pink or red oval rash. The rash may be accompanied by low-grade headache, fever, nausea and fatigue and itching. Topical and oral steroids are needed. Water, sweat, and soap may cause irritation and should be avoided in the disease. Topical zinc oxide and calamine lotion are useful for pruritus.
I feel that physical examination by a doctor is necessary to make a diagnosis. I hope it helps. Take care and regards.