Lmale- I did study a bit of nuclear physics and I can tell you that the assertion that in stars, hydrogen is indeed fusing into heavier elements. To study up on the subject I invite you to google mass defect, binding energy and, the binding energy curve. Mass defect is the phenomenon where atoms have slightly less total mass than the sum mass of their components. Binding energy is like it sounds: the energy required to keep two or more protons together in an atomic nucleus. Protons have a positive charge and tend to repel each other just as they are attracted to electrons which have a negative charge. This is known as the electromagnetic force. The basic hydrogen nucleus has only one proton but, every other heavier element not only has more protons but neutrons as well. Neutrons have more mass than protons (about an electron's worth) and have a neutral charge. Giving up some of that little extra mass in the neutron as energy keeps the nucleus together is the binding energy. It is also know as the strong nuclear force. The strong nuclear force is stronger than the electromagnetic force but, has a tiny effective distance thus the need for neutrons and proper arrangement. The heavier the element, the more neutrons are needed to keep the nucleus together and, they start to out number protons in elements heavier than around iron and nickel. Remember that.

Sorry for the long explanation but, it's necessary. Anyway, we now have mass defect and, binding energy. When one expresses the equations for these two together, Einstein's famous equation E= mc^2 is derived. Energy is mass times the speed of light squared. In other words: BOOM! or, a shitload of energy. When you look at the binding energy curve, you'll notice an extremely sharp differential between hydrogen and helium and, a gradual downward slope from cobalt on up. The differential is where the energy is. Fusion is more powerful than fission. Most elements reside at the top of the curve. They are stable. The radioactive, heavier elements are unstable tending toward stability thus decay. Hydrogen is stable but, has the potential for the release of incredible energy through fusion to helium and, because of the initial stability, fusion is a harder reaction to start. Because of the binding energy or, lack thereof, all elements tend to want to become iron through nuclear fission or, nuclear fusion. (refer also to the table of the nuclides)

When we look at the nature of matter and energy, this is how they are related: Matter is stabilized energy. Energy (in the nuclear sense) is a differential in the stability. Quantum theory is better for explaining subatomic phenomena including how matter formed from energy. Chemistry is the study of matter ( properties, reactions). Albeit true that a small amount of anti-matter is formed in stars, too much of it would result in star annihilating themselves. Hope all this helps.