Pls help

Sunday afternoon me and my boyfriend had unprotected sex and although he says he pulled out I’m not going to trust his word over my body. He finished very quickly because he said he hasn’t had sex since August. I’m not on birth control of any kind and being a senior in high school this makes me very nervous. I got very sick last night from what I’m sure is good poisoning but he and I are very nervous. I don’t want to tell my mom until my period is late but I can’t afford the plan b pill. What are some at home remedies I can do to help prevent a pregnancy? I drank vitamin c all day yesterday but now I feel to sick to eat or drink anything. Please help with any advice you can give.