Unwrap doesn't work properly I've been working on a model and I want to unwrap it in order to apply textures.

Problem is, when I click on "unwrap", the model doesn't take all the space available, and some parts are stretched in a very weird way, even tho (I believe) the unwrap was done correctly, and anyway I think it'd be impossible for it to look like that, even if I made a mistake.

The scale is 1 1 1 (I've applied both rotation and scale).
Furthermore, when I click on "unwrap" once again, nothing changes, it looks like it is stuck, somehow.

Any ideas?
Thanks.


this is the stretched part of the model. As you can see,it's basically a cylinder, and you can notice my seams.
Go into orthogonal view
Go to the front view
Select the front faces
Go to UV and choose project from view
Rinse and repeat for the back and if necessary sides. 
Remember you can select the individual UVs and move and scale them on the uv map.