"Taylor felt he wanted to take the relationship to be too public," a source told E! News Tuesday about the 26-year-old singer, "and she was not happy about it and thought it was too much publicity."
Us Weekly quoted an insider as saying Hiddleston, 35, is now "embarrassed that the relationship fizzled out."
"It was an intense start," another person told Us. "No one can keep that kind of momentum going."