need some advice

This Thursday I lost my virginity and while the event itself was uneventful, I left feeling quite anxious. The boy I lost it to is 3 years older than me and seemed to think my anxiety was completely irrational, but I think its warranted given the situation. I'm still in high school and am very concerned about getting pregnant. I made sure he wore a condom, but he put it on the wrong way at first and had some precum on his tip, and flipped it around, I made a comment, but he assured me he'd done it before without consequence. But here's where I reach an issue. He may have done it before, but Thursday was my first day of ovulation. I watched him take the condom off and there seemed to be no leaks, so I'm not worried about that. But I am worried about my chances with the precum and my ovulation. One of my friends brought over a couple doses of birth control for me the day after, not the smartest I know, but I still can't help but worry that I might be pregnant... Should I really be worried or is there nothing to fear? My period is supposed to come until the end of July and I'm struggling to wait that long. I could really use some advice.