Do not Panic!
Gravitation is right in that the first test could be notoriously false. In fact, there is some opinion in "some" scientific community that a false positive can happen very easily, and can be caused by many many factors. These could range from a common cold at the time of test, to a flu, or a flu vaccine or other unrelated health condition that could raise the level of antibodies in the body, which could in turn influence the hiv test.
Indeterminate results can also happen because of some antibodies to some other condition (not hiv) reacting to the tests and is usually not a huge concern.
Worst case scenario, if you repeatedly test positive, take it easy, and take charge of your health. I have a friend who is in the medical profession and I can get you some answers if you wish.
Good luck!!!