Employment bond

Hi Ma'am/Sir, I'v been working in a company for past 11 months ,where i had joined as a fresher.They made my parent to sign my bond with the company,in a bond paper ,for 18months.Bond amount is 1lakh rs. No training was provided during initial 6months(they mentioned in the bond that they would).We were asked to google and study under the guidance of other seniors at office. We were not given a copy of the bond, but in another document provided its mentioned like: "After 18months of continuous service to the company you can terminate your service with a 3 months notice period " So i will have to stay 18+3 months in total? The work stress is too much more than i can handle,and i had been dragging on,coz i know if i quit they wont give my experience letter and all my hard work will go in vain.But for the sake of my health i would like to quit the job and i hope not to join an IT company again.So will my experience letter have any much importance.I'm just 1 year out of college. Please help me how to leave the company without much problem.