Education time!
[spoiler=Gross]Every month, the uterus sheds its lining. This lining drains out through the birth canal as glops of blood, mucous, tissue, and other gross. This gross can last anywhere from a few days to over a week of leaky gross, crampy gross, and more gross.
Due to the contractions of the uterus, and even opening of the pelvis, you can get cramps that are either mild or horrible. These can be accompanied by bloating, fatigue, nausea, gas, and more gross! If you're really lucky, you'll be leaking from every hole!
Each month is different. Sometimes, it comes and goes and you don't really think too much about it. Other times, you're laying in bed, wishing you were dead. It's gross and I certainly won't wish it on a FICTIONAL character.[/spoiler]
The "moonsickness" line is from the term "moon time," a Native American description for when various tribes believe the uterus-owner to be either more powerful, or contaminated during that time of the month.
"Moonsickness" is a modern variation. However, historically, the term was to describe someone who was deemed "crazy" or a "lunatic," and thus could be applied to all genders.
If you want Toshi to have a were-form, that's fine. But I'd avoid the monthly visit from Aunt Flo.