I Am A 17-year-old Girl. When I Was 4 I

I am a 17-year-old girl. When I was 4 I had an ASD repair. This summer I passed outNow whenever I stand up I feel like I am going to pass out. I feel dizzy and everything turns black except for where I am looking (tunnel). The same feeling when I passed out during the summer. I am also always tired and never feel like I am rested. I can go for a name at any time. I also have ADHD if that helps