B.Tech Career Counseling

I appreciate your sense of approach. Answering your question. Changing a branch is up to you my friend (my personal opinion is to not to change the branch).
But before you opt for another branch, keep an eye on various subjects and your interests upon the subject. It's your future and your own life. So, you should be aware of your interests and take a branch according to your interest. Talking about your preparation which you did in these 3 years, it doesn't mean the struggle you had is useless. Remember, every experience gives you the new technique and new ideas. So, never lose hope and keep trying.