I cant get over my girlfriend who passed away

Im 17 and my girlfriend of 2 years passed away. I keep thinking about her even though I know I shouldn't. Every little thing reminds me of her. My heart hurts sm and I dont know what to do. My father tells me that there are so many other girls out there and I have my whole life, but me and her made so many promises together and planned our whole lives out together. All my friends just think I'm corny for being sad all the time. I blame myself for her death when I know it wasn't my fault. I just need something to blame. I miss her so much, and I really just need any kind of advice, because I think I am overreacting.