It sounds like your doing a fantastic job with this tiny kitten! : )
Young kittens do mainly sleep, eat and eliminate. If she's closer to 3 weeks old, she should start moving around a little bit by herself, and also, at 3-4 weeks of age, you can start introducing a soupy mixture of KMR and quality canned kitten food. A kitten this age, should eat every 2-3 hours, as, if she were nursing from her mom-cat, it would be basically around the clock. After eating, you can gently burp her by holding her over your shoulder, like a human baby (place a towel on your shoulder) and gently tap her back.
Yes, you should be waking her to feed her, if she doesn't wake up an meow for her food before 3 hours, and if you feel she's acting too sleepy all the time, an evaluation by the vet would be a good idea, at this time, just to have her checked out and make sure all is well.
If she's eating well, gaining weight (has a rounded belly after eating), has no problem with urination or defecation, she's most likely fine. Make sure that she's responsive to you and interested in playing, a little bit, with your finger.
The following sites will help you with information re: hand rearing kittens; they concentrate on newborns, but do give info about older kittens, too, so I think you'll find this helpful.
If you have any doubt re: if she's eating well and/or is healthy, definitely have her checked out by the vet, ASAP.
I hope all will be well!