This may not be the right thread to ask this in but it's right enough I suppose.
No, the standard model is just three forces (electromagnetic, weak, and strong) plus gravity. A fifth force would be beyond the standard model.
I loosely associate forces with bosonic fields -- photons for EM, gluons for strong, and something confusing for weak. But then no one seems to want to call the Higgs field a "force".
Here's one incomplete answer:
> Q: Why isn't Higgs coupling considered a fifth fundamental force?
> A: The Higgs exchange between matter particles can certainly be called a force. Whether it can be viewed a fundamental force, is a matter of taste. But there is one important distinction between the force due to the Higgs exchange and the usual fundamental interactions. The strong and electroweak interactions are described as gauge interactions. It means that they are not put by hand but arise automatically when you require that the matter fields be invariant under local certain internal transformations (phase rotations, color transformations, etc.). In contrast to that, the "Higgs force" is put into the model by hand, as its presence is not driven by any symmetry consideration. You can equally nicely consider a model with zero Yukawa coupling.
http://physics.stackexchange.com/questions/1080/why-isnt-hig...
If they are not fundamental, does that mean physicists suspect they are complex interactions of other, fundamental forces?
And yes, the non-fundamental forces (like friction) are complex interactions of fundamental forces. For friction it's the sum of electric forces between atoms. The important point is that an atomistic model of friction gives you an essentially unsolvable problem, while the effective macroscopic model of friction is high school stuff.
But the effective formula that the magnitude of the friction force equals a material constant times the magnitude of the normal force from the plane onto the brick gives you a very simple model (solvable with pen and paper).
edit: good example discussion
http://www.scientificamerican.com/article/dark-matter-modifi...