whenever i talk to my follower and tell him to do something, it goes back to the dialog strand where i ask him to join, and when i first enter the strand where i ask him to join, i have to aks twice!
If this is a dialog that you wrote, it sounds like you may not have the jumps in the dialog set up properly. You also need to have an IF statement in your follower's dialog script that checks for his status as a follower and starts the dialog at a different line once he has become a follower. Most likely you are starting your dialog at line 1 every time you talk to the follower because your script doesn't have that IF statement and the followup statement to start on a more appropriate dialog line. Dialogs and dialog scripts aren't exactly automatic nor are they always intuitive unless you've done a lot of programming.
re-script/get dialogue editor I think you should get a dialog editor, like Zammy's. I personally have 2 dialogue editors Grant Davis's (which is VERY useful for just the wording) and Zammy's which is very useful for the effects that saying this line will have. You can get both from Darkunderlord's site.