I feel like a horrible friend :'( HELP ?

Ok so me and my friends went to concealing and my friend started crying when she was talking than m other two friends started crying because seeing her cry made them cry but I didn't cry and it makes me feel like a bd friend and am not :'( same thing happens when somebody die's like a family member I never ever cry except my grandma when she died which wasn't long ago and it toke me time to cry because I didn't want to fake it so I just let it come to me by the way everybody was looking at me like whats wrong with that girl why isn't she crying andI would of thought the same since I grow up with her and I don't understand why was it so hard for me to cry like I mean I saw mostly my whole family cry and I just stood there for like 8 mins and than I started crying I don't know whats wrong with :'( do I have a problem with crying ? because every time someone Doe's I don't know why but I take out my feelings in the night when am sleeping I guess is because i don't like it when people see me cry :// I don't know someone please help me and tell me why am like this I feel like a horrible person that's selfish and I don't want to be selfish and a bad friend :'( help ?