Internships, summer placements at a research laboratory and involvement with applied research are the things that can counterweight your "low" grades.
These activities will be helpful in two ways:
- they provide you a contact network (simply getting in touch with more people, active groups in the research world are always on the look-out for fresh forces)
- they show your motivation to work in a certain field (yes, it is an important consideration).
The grades show what you achieved, your potential may be higher, who knows, and who cares: please note that contrary to the general feeling in the Physics world, the world is not divided between uneducated barbarians and potential Nobel prizes, there are a lot of top-notch head of research groups who would not get a Nobel prize in a thousand years.
If you try hard in the next semesters to look for internships&similar things and you do not manage any, well, it may be an independent assessment that you are not cut for the abstraction required in physics. This leaves the door open for you to get your feet wet in the thousands of applied fields that require a good understanding of physics (irrespective of your definition of "Physics I enjoy" you mean Newton's second law, Partial differential equation, thermodynamics, rational mechanics, etc ... don't worry, there is a niche waiting for you if you survived the bachelor exams without much commitment).
