job prospects and challenges for a biomedical engineer

Hi Nurfarisya,
I can completely understand your confusion about the job prospects and challenges in the field of biomedical engineering. Having narrowed down my own specialty from biological engineering to biomedical, I have been in your position too and I would be glad to answer your question to the best of my ability.
Biomedical engineering is divided into different specialties. While more may evolve during the next decade, currently it's divided into bioinstrumentation (knowledge of computer science and electronics to make devices that diagnose or treat diseases), biomaterials (fabrication of materials to design implants and medical devices), clinical (healthcare related) and systems physiology (to understand how living systems respond to environmental changes). While these are specialties, they are still pretty broad and you can find a variety of jobs depending on the specialty you are interested in and the place you want to work in. I live in USA so I know more about what it is like here.
As for me, my specialty in my PhD program is biomaterials. I design and fabricate materials that can be used for blood related devices like catheters and antimicrobial coatings for implants. You need to have a good knowledge of all the sciences to succeed in the field. I like biology and chemistry equally so it is not very hard for me. It is a very interdisciplinary field and hence you will need to relate your courses with each other. Once you succeed, you will have many options to choose from :)