I need advice

I’m 17, turning 18 next week. I feel like I’m drowning at the moment because I’m worried that I may be pregnant. I have a very strict mom who doesn’t see me as an 18-year-old but only views me as a 12-year-old. I had a guy that I really like but for some unknown reason…she hates him. He treats me so well but since my dad divorced her, she’s been bitter and stricter on me. I have two younger sisters (14) and a younger brother (4) so it can be directed towards me the most. Since last Tuesday, I haven’t been feeling ok and then David (The guy I like) came over to comfort me. Me and David are both students but he has a much more busier schedule than me so this was the first time we’ve seen each other in a long time. We ended up having sex before he left and apparently, it was unprotected. Today is suppose to be the day I get my period and the wait is terrifying. I’m actively worried that I may be pregnant…I have no money to get a test and I’m scared. What do I do? Am I just overthinking the pregnancy thing? I don’t have a mom to turn too.