To select any engineering course it is not prerequisite to know  the basics of that course . You can learn that in your college life also .I am from computer science department bt before joining college I don't have even basic ideas of computer science bt after one year I am quuqu confident about the course. So without any fear you just select that branch in which you are interested.

I am interested in maths

Computer skill is not necessary for every engineering courses.

Core engineering branches like electrical , civil , mechanical has got computer programming in their curriculum once or twice.But it is attainable.it is better not to chose electronics and communication since it is closely linked with computer programming.

New btech branches like chemical engineering, food technology,

I am a civil engineering student and was not good at computer science .I dont feel it difficult .

Opt for the choice only after knowing what your passion actually is and the field you would like to work after.