JWs are trained to over react they always blame the perceived sinner. In a reasonable life what you do with your boyfriend is strictly your business and no one elses. Don't let them make you feel unworthy or shameful. Actually you don't deserve this treatment and their hysteria is a shameful display as it relates totally to how your behaviour reflects on them, What about your right as an adult to privacy?. What about the trauma they are putting you through?
I am so sorry that this has happened how you approach it is still in your control and others have made suggestions. But remember outside JWs there is a different perspective and you do not need to be defined by them.