You are scoring about 50% marks of the total which is quite good. You can easily get CIVIL in any of the three colleges but it is less probable for you get MECHANICAL at BITS PILANI though you can get it in other BITS. One thing more I would like to say that dont opt for BITS GOA or HYDERABAD because they have a very poor exposure and placement. YOU might get Mechanical at BITS PILANI.
Hope for the best.