Recentry I left company without serving notice period

I used to stay at a place 18 km from company(joined company on feb 2014), in OCT 14 i shifter to a place 33 km from company. I used to be ill most of the time due to long traveling hours and 9 hours of work accounting to 13 hours minimum a day, i used to have holiday on 2 and 4 sat in company. I resigned the company in dec 2014 but company didn't accepted my resigned even after serving 2 months of notice period, at last when i understand no option left with me i withdrawal my resignation. My health keep on deteriorating and hence i resigned again in 28 April, 15. I was in lots of tension and ill health so one fine day I walk off my company on 16 may 2015. Now company has send me termination letter with below text , I am bit scared and not able to think on it, they are not releasing my relieving and experience letter. Please help me out ============================================================================= Your services are terminated from 16th May 2015. You are directed to handover all the official documents, information, data, software codes, diagrams, data in whole / parts or in copies and photocopies in your possession latest by 20th May 2015. This is to inform you that you have signed employment agreement and confidentiality agreement. We wish to remind you that breach of these agreements would lead to criminal and civil proceedings.