We skip school and head to Lily's house

After a horrid few awkward seconds pretending to be who we were with people who passed by, Lily grabbed my now weak arm and tugged me away from the school.

"Stop it, Lily, it hurts!" I squealed.
"Don't call me that, people will get suspicious. Call me Tom," he growled, letting me go.

Once the road looked deserted, we slowed to a walk.

"What just happened?" Lily, now Tom, asked in a whisper more similar to her previous female self.
"I have no idea..." was all I managed to say.

We soon arrived at Lily's house, and Tom grabbed my bag, easily finding the key, and let us in. We went up to Lily's room and sat down. After taking a few deep, shocked breaths, Tom looked at me.

"I don't know what happened, but we can't let anyone know or they'll laugh at us, and if we can somehow prove we switched they'll just take us off to some lab to be researched!" Tom said, looking scared. I nodded in agreement.
"We have to assume each other's lives till we can find out who or what caused this to happen. I think I can handle myself, I've got a brother, and from what I've seen being a boy isn't too difficult to learn. But I've got a lot to tell you, some of it is normal for a girl, lots of it isn't," said Tom.
"What sort of things?" I asked, curiously.

"Okay, first, my periods are due very soon. You have to be ready to use the tampons, which are in my bag. If possible, try to get me to help in private. There's a lot of things that will be difficult, but don't be afraid to call me. Also, there's something else..." he said, looking nervous.
"What?" I asked.
"My brother... he sometimes comes in and forces me to have sex with him. He threatens me about telling something to a certain someone if I don't. Please, for the sake of our friendship, don't let him tell you what it is. I hate to **** this on you, but please just do it with him and get it over with!" said Tom, hurrying out of the room before I could answer.