My kitten is sick! HELPPP!?

About a month and a half ago, two very adorable kittens showed up on my doorstep. They couldn't have been more than a few weeks old. We named them Lois and Clark(one is a boy, one is a girl). Lois, who is normally very energetic and always exploring(hence their names), has been extremely sick for the past couple of days. She is lethargic, and she pretty much refuses to move unless you move her yourself. For example, I sat her on her bed, and she just stood there, falling asleep. I laid her down, and she would not move at all, not even when little Clark came to play. She has a very warm and dry nose, but her feet are relatively cool. She is constantly purring, but from time to time she will sneeze. I am extremely worried about her. She is an outside cat, so ticks are probable(I found one on her just a few minutes ago, but it was small), and they have probably had fleas, too.(I just gave them a bath the other day) Any help would be amazing.