Yes, you have to repeat the intermediate course with the science stream taking Physics, Chemistry and Mathematics as one of your options and the other option could be Physics, Chemistry and Bilogy. There are some aspirants persuing 10+2 with the combination of Physics, Chemistry, Mathematics and Biology simultaneously from a recognised Board so as to be eligible for D. Pharm course.
Repeating the same by being a regular student of a school would affect your current assignments being persued and hence it would be a wise step to undertake this course from IGNOU or from any other distance education mode. However, ensure that such a distance education mode is the recognised one in terms of its affiliation.
In order to take admission in D. Pharm, you will have to pass the entrance test conducted by such institutions and your age should not be less than 17 years. The entire course duration is of two years divided in four semesters. Some of the best institutions are BITS Pilani, Punjab university etc.
Switching over to D.Pharm course would take its own time at least there will be an extension of additional two years for acquiring the diploma where as your B.Com degree would open plethora of options such as taking up probationary officers examination of the Banks, LIC PO, taking up MBA from a reputed institute or even you can persue M. Com for your better prospects in teaching line. Analyse pros and cons prior to switching over your track.