Slightly enlarged under arm lymph node?

All of last week i didnt have a problem.It wasnt until last saturday,that i felt some pain in my right armpit.I went to the er, and the Dr felt around and said that i had a slightly enlarged lymph node.He ran 3 tests,An ekg, xray,and a cbc blood test. All tests came back normal.He told me that it was something called catscratch disease.I told him that i wasnt scratched my any of my cats.He said that it doesnt have to always come from a cat.He said some bacteria may more than likely is causing this.I had a foolow up with my Family Dr.He said the same thing.I even went back to the Er this past wednesday , and those Docs over there said the same thing but drew no blood cause they said it made no sense to do it since i had one on sunday. She gave me zithromax. What made me go in the 3rd time was because i started feelin pain in my elbow. She said it was tendonitis. I know i sound like a hypocondriac , are all 3 right?

I originally thought of lymphoma. But all the Dr's said that in order for it to have been that , the nodes would be larger , and not hurt whatsoever. Mine are like pea sized. Is this true also?

"I told him that i wasnt scratched my any of my cats"

Cat-scratch fever is caused by a bacteria that is on the claws of a cat, so you wouldn't necessarily have to be scratched to contract it, and it can also be carried by ticks