I was my bf sideline

Me and ny bf have known eachother for 3 years but only in a relationship for 1 he never wanted to settle down we spent lots of time but never got the title now years later come to find out when i met him he had already had a gf which is why he was bull crapping at first, should i be mad about this news or should i let the past be the past, mom always said the same way you got him will be the same will you lose him