Should I drop out of S.Y.BCom and get into F.Y.BMM because I know that I cant pass in BCom and that I am interested in BMM?

No doubt that you can do that (if there are colleges who are ready to take you, or have seats in BMM), but before you take that leap its important that you take a look at the syllabus of BMM.

It will help you decide whether you will be able to cope with it or not.

And secondly you also need to look at the career options available after BMM.

For that you can log on to http://www.youngbuzz.com/careers/career-options

Check the section on media and communication here, which will give you details on the careers, its scope, remuneration, career map, opportunities, requirements etc.

Go through it and let us know what have you thought about it.