As long as you eat well and breathe well and are in general good health, your body produces all the energy you need to survive. If you feel otherwise, visit an acupuncturist.
You can cultivate more control over your energy field through any number of techniques: qigong, meditation, tai chi, yoga, etc. When a person's energy mixes uncontrolably with others in their presence, that is called "blending," which is somewhat sloppy and bad for your health. Know where your personal energy begins and ends. This awareness can be developed through practice.