Immediately after conception, your HCG levels will begin to rise. The quickness with which they begin to rise is highly individual, so you may or may not be able to tell after five days whether or not you are pregnant. Some tests are more sensitive than others, so see your doctor or choose the most sensitive test available.
No, the earliest you can test is seven days after ovulation. Even seven days after ovulation results are not accurate. It is best to wait a few weeks to test.
Yes, in fact many women can confirm their own preganancies immediately after conception. If you are trying to become pregnant, many tests on the over-the-counter market can pick up the hormones within five days, even if you have not missed a period. Of course, a blood test is more accurate so consult your physician for confirmation.