I feel fine. Do I really need to take medicine for latent TB infection?

Yes because. The idea of treating latent TB is to make sure it never becomes active. If it ever becomes active, you will get really really sick. Better to take one drug for 9 months, then be deathly ill taking 4 drugs.
Yes. The purpose of the recommended treatment is to prevent you from developing active tuberculosis when you can afford it the least, when you are older and sicker. It also helps break the transmission of TB so your loved ones would not get it from others. Finally, the risk of taking the medications increases with age. Take it now, reduce your risk for later.