I have not mentioned myself as a EWS candidate while filling the TS eamcet application form ,can I now use it while counseling

Hello,

No, you can't. You will be treated as same category candidate that you mentioned during application process. Like if you applied as General candidate then you cannot take benefit of EWS candidate even if now you have the ews certificate because you have been registered as general candidate in the records and now it cannot be changed or altered.

I hope this helps.