Eilen
You describe classic symptoms of shingles. I've had them twice, 20 years apart, once on my back, last time two years ago, on my face and nape of neck. You can quickly narrow your choices; If you've never had Chicken Pox, you don't have Shingles, it's the same virus. Interestingly, my shingles weren't rash like, rather a spot on my back, right where I couldn't reach it, silver dollar sized, then I finally went for the diagnosis. I thought I had been bitten by an insect. Prednesone did it, relief within two hrs. and gone as quickly as it came. This last bout started with small lumps on my face, down the side of my face and under the chin and around the back of my neck. The pain was excruciating. This virus follows a nerve, and clasically it goes around one side of the body as you've described yours. And who's to say you don't have both problems. Attend to the Shingles first and foremost, the ramifications from that problem can be more dibilitating than costochronditis. Good luck.