Am i having MOOD swings? i was okay and just started crying. please help?

well iwas on youtube and EVERYTHING was fine and all of a sudden igot this sad feeling and pressure onmy chest and was thinking "inever want my mom to die" nd istarted crying and still am kinda. nd italked to hur nd cried . nd all of a sudden ifeel bad 4 how itreatt her buh usualy honestly idont care . buut it got me sad cus shes old age (62). idk wat just happened. wat do you think just happened?