Explaining your chronic illness is a large mine field I'd avoid as much as you can. You're not going to get preferred/special treatment because you were sick.
Did you apply to more selective universities than your friends did? I'd recommend double-checking your references, admission materials, transcript
, and other forms you submitted for errors. Contact admissions offices for explanation, if you can. Improve weaknesses for the next semester, cast a wider net and apply to a wider group of universities. Not getting in on the first desired semester is fine, try again and you'll succeed
![:-)](/community/emoticons/smile.gif)
Good luck,