I'm glad Clark told Lois the story about Lena (though he left out the Superman part). These memories were eating away at him and he needed to get it off his chest. Although Lois thinks she isn't sensitive, she was sensitive enough to know that something had hurt Clark and to wait until he was ready to tell her the truth.
And now that they are going to investigate the illegal arms trade together, I imagine it won't take long for Lois to put two and two together and find out what Superman was doing in the Congo one year before.
Eagerly waiting more.
Andreia