please help

mi

This post might be long but please be patient and read...am a lesbian,and i love my boyfriend soo much,she is the best,always being there for me when i need her,the perfect partner in the world,weve been together since middle school.there was a guy who was pesturing me since high school that he loves me..i dont even look at him twice because got no feelings for guys..Note(my step dad raped me),so am scared of men and my boyfriend knows.So this guys really makes me uncomfortable in school,but later we became co-workers because we were both entertainment prefects in school,and had to work together.Along the line i had problems with my boyfriend.To cut a long story short.I got into a relationship with this guy,and he really changed my perception about men, i told him about my step dad,this guy makes sure am never sad and had no problem,but i never told him am a lesbian,on a holiday he took me home to a family party and i met his mom,and when his sis came guess what?,she was my boyfriend.I thought she was going to react but she pretend we never met before,after she left her bro told me his sis is a lesbian 😂 i should be careful. what do i do now? what if she tells her bro. because she really got drunk that night and promised to commit suicide when i dont leave her bro.That she loves me more than life itself.But i cant am soo much into her bro,and dont want to cause him a little pain.What do i do now? what if he gets to know.