Justin Bieber announced on Instagram that he is battling Lyme disease.

He also announced that he has a serious case of mononucleosis, which has affected his skin, brain function and overall health.

Bieber said he plans to reveal more details about it in his upcoming docu-series on YouTube.

He says it's been rough couple of years, but that he's getting the right treatment and will be back better than ever.

MORE:  See Justin Bieber's Instagram post