My dog is scared of everything?

She is a three year old and as she's gotten older, she seems to have grown more scared of everything. Every Friday night is little athletics close to our house and she hears the starting guns and goes crazy. She shakes uncontrollably and pants heavily. When she gets in these moods, she scratches on our gl door and jumps all over you. She's scared of broomsticks, dog bowl's making clashing sounds, fireworks, toy dogs...EVERYTHING!! Could she have been previously abused? I got her from a foster home (they had rescued her). She never used to be like this up until about a year ago. How can I stop it? What if we go on holiday and she has a heart attack?