Antidepressants
He takes a TCA for his depression. Common side effects are:

. headaches
. dry mouth
. blurred vision
. digestive issues, such as stomach upset, nausea, and constipation
. dizziness
. drowsiness
.trouble sleeping
. memory problems
. fatigue
. weight gain
. sexual problems such as low sex drive, erectile dysfunction, or ejaculation problems
. trouble urinating
. fast heart rate
. sweating

     Jaehyun hates the side effects of his medications, but he's unable to get a different one because the problems of this one aren't serious enough, according to his doctor. So he just deals with it.

     Part of the reason he hates it so much is that he already has a shy bladder, so he doesn't pee at school, because he literally can't. He already has bedwetting problems, and his medication making it difficult for him to pee doesn't help this issue in the slightest.

     He also has issues with his weight to begin with, so whenever he starts to gain weight, he starts eating less, which only makes his sleep problems, memory problems, fatigue, dizziness, and nausea worse.