No if you are obc you can not claim ews seat because you have to show general caste certificate(surprised) to claim ews seat 

What is your ews rank??

If you belong to EWS, for the jceceb jee (main) application, apply in OBC category if you have the category certificate with valid proof. Otherwise go with the general EWS if you have valid documents ready for it. Do not apply without the documents as you would face trouble in seat acceptance and councelling. Also, please go through the latest formate of the caste certificates and get it in that parcticular format only otherwise there are chances that you may get rejected due to invalid documents.