I am gonna give my 12th CBSE board examination. But I am very much worried about the stream I'll opt after tha?

I am in commerce streame (with maths). After my 10 board examination I wanted to opt science streame but due to some reason I am in commerce....Now I wanted to go to some science field or computers..is this possible? Please suggest me what should I do now (except BCA)...And also tell which is the best college of BCA in India?