For the first year or so of my life I was really sick and had all kinds of problems and illnesses, this put me behind developmentally wise. I've realised I have a ton of the symptoms of adhd and I was just wondering if that could've been the cause of it or is adhd a condition that your born with?
Probably both. We’re not 100% agreed on what exactly causes ADHD, and it’s hard to say for sure whether we’re born with it or not since newborn babies don’t really do enough to be able to tell if their behaviour is typical of ADHD or not. I know some researchers are currently working on a project that aims to find very early signs of Autism and ADHD in infants. It is generally accepted though that if we’re not born with ADHD, then it’s something that happens very very early. However, research does show that ADHD is highly heritable, which is a sign that there is a strong genetic component. Most likely it’s a mix of genetics and environmental factors.
It’s possible that you had a genetic vulnerability for ADHD, and that the environmental factor of you being sick as an infant increased your chances of getting ADHD. The developmental delay this caused probably also contributed to it. DSM-V (the official diagnostic manual for psychiatric disorders) mentions that infections in childhood (like encephalitis, for example) often correlate with ADHD, even if they’re not sure whether it causes it or not.
Either way, don’t be afraid to see a psychologist about it. Being sick a lot as an infant doesn’t necessarily exclude you from having ADHD.