I sometimes have disturbing intrusive thoughts and also have a ritual of checking closets and windowsills at night, and paranoid thoughts. Help?

What to do.. The best help is to see a mental health professional for a complete evaluation. Talk with your parents to make sure they understand what you're going through and are supportive. Then either your parents or you can speak to your pcp to explain what's going on and ask for a referral, preferably someone experienced dealing with teens. I hope this helps you to take the next step. Take care.