Hmm to me, it sounds like a problem with dream control. Remember that lucidity is not equal to control You may be lucid and be sure that it's a dream, but dream control is an entirely different thing. I think that is why your dream environment started changing on its own, and you couldn't get things to happen the way you wanted them to.

Don't worry, dream control comes with practice, so you should be able to get better at it. Here are some links:

http://www.dreamviews.com/f14/dream-...utorial-66753/
http://www.dreamviews.com/f14/dream-...tml#post451252

The second one is a bit lengthy, but it is very thorough, and really worth reading! Good luck and happy dreaming~