Is energy always conserved?

OK so I have a theory on dark energy that would work with conservation of energy. First, if the energy of a system is conserved, the loss of energy in light through expansion could explain part of the dark energy. Then add in some quantum mechanics. If I recall correctly trying to separate quarks puts enough energy in them that the actually form new quarks and bonds between the new ones. what if not all energy transfered into the quarks and bonds? That could add in another amount of self sustaining and increasing dark energy. Granted I'm not fully educated on any of this, so I'm always ready to hear counter arguments and thoughts. My second hypothesis in this is that due to conservation of energy, eventually all methods of transformation of energy will be used up, making all energy dark energy. If conservation of energy was implemented in this scenario there would be no energy to transform to dark energy and it also couldn't expand further because there would be no energy to convert and thusly would break conservation of energy should it keep expanding at an accelerated rate, but actually slow down as the now maximum dark energy would become more spread out through the system.