While some people do experience bleeding after vaginal intercourse (something can happen the first time or the fiftieth), four days of heavy bleeding like you describe is not a normal outcome. Usually, if bleeding occurs it's because a small cut or tear formed inside the vaginal canal from things like lack of lubrication or lack of arousal. That kind of bleeding is usually light, and only lasts a day or so. If you're certain this isn't a period, then you'll want to check in with a healthcare provider. Is that something you know how to access?