Sherlock is thirteen, and he can't sleep.
He's been waiting for it to come for three days. All the warning signs are there.
~~~
It finally happens when he is in the shower, trying his best to ignore the slight hints of curves his body was getting.
As expected, a dull ache begins in his lower abdomen, slowly building until it feels as if his belly is being carved open by a sadistic murderer.
Sherlock tries his best to ignore it, but it persists, causing him to clench his teeth.
He goes through the motions of rinsing shampoo out of his hair and washing soap off of his body, concentrating on anything but the pain.
After his shower, he raids the medicine cupboard for any sort of painkillers, and under the sink for the pads his mother has bought for him.
He won't touch the tampons.
A handful of pills and a pad later, he lays on his bed, staring at his ceiling fan in wonder.
He finds he likes the feeling of drugs coursing through his system.
As Sherlock's cycle goes on, he finds himself relying on the pills more and more to function around the cramps.
If Mycroft sees what is happening to his younger sibling, he doesn't say.