If I have a positive TB skin test, does that mean I have tb?

Not necessarily. (+) PPD means that you have been exposed to the TB agent. It doesn't say when. So if you had the TB in the past, it still will be (+) because your body "remembers" from the previous exposure. The greatest risk is if the TB agents are latent in your body, that's why everyone with a (+) PPD will have either a complete treatment with 4 medications or a mild one with only one. Your PPD will remain (+).
Yes . A truly positive PPD means that you have living tubercle bacilli in your body, but not necessarily active disease. Having had a primary but unrecognized case of TB causes these organisms to be contained by your immune system and gives a positive test. The importance is that if you need to take medicines which impair immunity these organisms can be let loose and create active disease.
Only a screening. Ppd is meant to detect persons that "might" have tb. You must talk to your doctor about doing a chest x-ray and further blood tests in order to confirm or rule tb. It is definitely very important not to disregard a positive ppd, but don't panic. It might be falsely positive.
POSITIVE TB TEST. It does not tell you if TB is active or not. Next step is chest x-ray to show the infiltrates if positive for infection.

Related Questions

What does it mean if I have a negative TB skin test yet a positive blood one?

IMMUNE PROBLEM. Both tests detect prior exposure to TB. A situation of diminished immune function, called anergy, can make the skin test appear negative. If you have a positive blood test you will need to have a CXR to exclude active infection and may need prophylaxis . Read more...