Everything has its own energy. Everything has its own source. So your aura is your own energy, and depending on the color, it shows you what you're currently being affected by. You are your own source of energy.
You can do things to cleanse your energy and make yourself feel newly cleansed and fresh. The simpest thing is to take a bath or a shower. Sometimes people add certain things to their baths to relax them more. Like lavender, or eucalyptus. Meditating or chakra cleansing (if you're into that) is another good way to cleanse yourself. Simply running sage smoke over yourself while visualizing bad energy flowing out of your body is another good technique.
But, there is no one flowing source of power, or energy. Everything has energy and everyone has it.
I believe the body is connected to the very energy of the universe. So if you think in that manner you realize that the world around you becomes a source of energy. You can draw energy from it. The Hindu tradition of Pranyama uses the concept of energy being in the vary air you breath. However it should also be noted that your body has its limits of how much energy can be held or channelled through it. Over active chakras can be a bad thing as well.
Auras aren't an exact science. As already stated, they are your own energy field. The colors and strength of your aura can indicate if you are healthy and what personality traits you possess. It won't tell you where an outside energy source is. Just tell you about your own.
If you are thinking an outside source is making you more powerful everyday, I'm gonna bet it isn't actually an outside source. Its more likely that everyday you gain practice and realization of what you can do. This can make you seem more powerful than the day before but it is more along the line that you are unlocking what is already there.