I should say, things happened very fast for me. I failed the board exam thrice. I failed my family, my friends and those who believe in me for the 3rd tym. Dont know wat happened to me.
thrice- a bit old fashioned, but correct. However, I'd change it to 'three times'
tym- should be 'time'
Dont know wat- this lacks a subject (I), 'dont' should have an apostrophe (don't) and 'wat' shoould be 'what'