Well unfortunately his house his rules. You are old enough to get a job and start saving to get out of there but I would focus on school first and stay rent free as long as you can if that's possible. Are you on birth control? It may put his mind at ease if you were although pregnancy is not the only concern that comes with sexual relationships maybe he is gauging your maturity level and believes you to be easily susceptible to being taken advantage of by possible romantic partners. You are 18 so you are of legal age of consent and it shouldn't be his business. But if you're living in his home rent free he does have a little say in your personal life whether or not it feels fair