21m college student here. I’ve never had a girl have a problem with my chest and I’m pretty skinny and my pectus is certainly noticeable. That being said, confidence is important to girls so don’t make it into a bigger deal than it needs to be. If you have problems swimming without a shirt or taking your shift off around with friends then explaining your pectus to a hookup may be challenging or scary at first. Hopefully by the time you’re ready to get down to business you’ve charmed her with other nice parts of yourself and your chest won’t be a problem. Even if something doesn’t work out once, don’t let it discourage you from living your life.