I can understand what you must be going through, but at the same time one needs to empathise with your family, if they are upset there must be some reason to it. And the only way to find out is talking with them. You need to express your concerns and the reasons you feel for this changed behaviour, and ask them what they feel about this; express your worries and emotions and give them time and space to talk about this.
Meanwhile do not let this affect your future course of life and don't let the circumstances change your perspectives. Do not let this affect your relation with your fiance as that would make matters worse.