Hi.. perhaps u might be staying in any city or metro city where these kind of culture is quiet common. So you also might have seen or have become witness of so many break ups.  Every persons understanding for relation develope by seeing the people in society or by his/her own experience. Till now you are not in any stable relation where both have promised to live together like in  committed relationship by getting engaged or not married. In such situation possibility of your b.friend for getting attracted  for some another girl and breaking relations with you can mot be ruled out. I think in this condition directly express your concern with your friend. Join the party every time when he goes on party. Minimize these kind of party in absence of each other. Besides it decide whats ur expectation is  from the relationship. If you want to settle with him . Decide whether he is ready to go ahead. Then wait for them to get settled and side by side start involving your family number.