Hello siddhi,
Yes, surely you can. You can give the Board Examination for mathematics through NIOS(as already said in an answer). This way you'll be able to add mathematics into your marksheet.
And yes, it is possible. A friend of mine did the same thing. She was a PCB student too and had interest in engineering as well. She appeared for JEE Mains and Advanced too.
Hope this helps.
Thank you.