hi guys a quick couple of questions, i ve just started the companions quests and im supposed to go with one of them as he is to asses me to see if im made of the right stuff,when i agree to do the quest it says my currant follower(lydia) is replaced with this new guy. now does that mean ive lost lydia completely? or will she be lurking somewhere so i can carry on with her. also she seems to be a bit weak these days,i have to keep reviving her.do followers have a limit to what they can achieve?
and finally i dont seem to able to carry very much,i use heavy armour but seem to have got weaker? im not diseased.....i dont think thanks guys

Normally when your follower is replaced by another follower the old follower will keep carrying whatever it was carrying for you and return to where they would normally wait for you to pick them up. In the case of Lydia she will wait in Dragons Reach or in your house in Whiterun if you bought it. Also, I think followers level with you up to a certain level (which varies between the followers) but perhaps try to upgrade her gear if you didn't do so already.