How do I tell my mom that Im not straight?

It can be hard to deal with this because you really love your family and you want to please them but think about yourself and how lying about being someone you're not just to conform. You're hurting yourself more. Sometimes being yourself means you have to break a few hearts and hurt even the ones you love. They cannot and have no right to force into marrying the opposite sex if you know in your heart that you like the same sex, and marrying a man will never get rid of the fact that you're attracted to the same sex. It's wired in your brain and it's just a part of who you are, you can't shake that away no matter how many measure you take. You can make yourself feel good by the excuse of family but your mother isn't going to live that long and whether people end up loving or hating you for coming out life has to go on, that's just the way it is. Just come out and be straight with yourself, stop being ashamed of who you always be.