I think where you're having big issues, is actually with the paper.
It appears to not be toothed, but more a 'matt' type paper. This will make it near impossible to layer the pigment and get any kind of detail.
I love pastel, and find it quite easy to get detail with the sticks now - for the REALLY fine line work, I have a sand paper block and just shave off the edge of a pastel stick (hard pastel) to a fine line. Works a treat :)
Soft pastels on their own can be difficult and work much better as loose landscape type pieces - that is where to medium and hard pastels come in.
I'd be investing in a few sheets of Canson Mit-Tientes and working on that. It's a true 'toothed' paper that will hold a lot of layers - great for beginners! Also not expensive compared to other good pastel papers.
Once you get your hands on some Canson, if you can afford it I'd highly recommend purchasing a set of Rembrandt Landscape soft/medium pastels. They will cover nearly all bases for colours you'll need to get started - I use Rembrandt's in all of my portraits still, they are very good general use pastels.
With the upgrade in materials, you'll be able to get more coverage and add more layers. At the moment you're getting a wax crayon effect. This will go when you get the right materials to work with.
This is my first attempt at using soft pastels, this was done in Rembrandt soft/mediums, on the reverse side of Canson Mi-Tientes (don't do that, it's full of little squares!)
And one of my recent commission portraits
As you can see, its all about layers and getting a good coverage over the paper, you don't want bits of paper showing through the drawing.