Well, there are several questions which you have raised here, and you can go through the answers:
1. Score of 45.23% in HSC: Is not too good but at least you have not failed! This itself indicates that you can manage your studies. you can check if BSc courses in your area of interest.
2. Engineering field is not good: This is heresay and a wrong notion. Every field is good, since there will be some jobs at least. The studies are exhaustive, and you need to work hard here.
3. There are no jobs in engineering fields: Again wrong information/ There are jobs but only for those who are good. If a person is casual, not technically strong, it is difficult for anyone to employ them.
4. Family is forcing to study engineering: Because the family loves you and wants you to do well. Also because they must have heard that there are good job opportunities after doing engineering. You need to understand their perspective. If you want to do something else than engineering, then find out your interest, the scope of that field, the career paths, job profiles and job opportunities in that field. Once you have clarity, sit and talk to your parents and explain the field of interest to them. I am sure that they will understand your point of view.
5. Which field is better for me? An extremely difficult question, and only you have the answer to this question! Find out which field interests you more, what do you want to become ten years down the line, what is your ultimate aim in life. Based on these answers you can decide the field of choice.
Hope this answers your queries.
Autograph your work with excellence!