PTSD

I lost my sister tragically a year ago and saw her die infront of me. Ever since I am always alert and never put my guard down. I never get near strangers and get afraid when any man comes near me. Everywhere I go my mind makes up the worse case scenario and I get ready for the worst to happen. Today I thought someone broke in my dads car and yelled at them to stop. I ran inside my house and told everyone someone broke the window. Turns out it was my dad who just broke something from his car. Everyone got mad at me and I felt ashamed. I wasnt able to do anything to prevent my sisters death and many commented on news articles how selfish I was and laughed. Now I try to give it my all to prevent anything else to happen. My parents get mad when I open up how my mind thinks everytime i go outside but they just tell me to get that out of my mind. They as well get mad when i get a panic attack over what I think are potential dangers or dangerous person. I feel so embarrased that i panicked everyone today. I feel alone that no one understands the flashbacks and nightmares I get. Its exhausting thinking this way all night and day. i feel hopeless