Yes, you can always change your stream even after graduation. In case you are genuinely interested in designing clothes or learning garment/fabric technology, you certainly can pursue a career in fashion design. Once you complete B Tech in engineering, you can pursue a postgraduate or master's degree in Fashion Technology or Design. The Fashion stream offers a variety of courses.

In case you want to pursue the course from any government design college you will have to pass the entrance exam conducted in order to enroll in NID or NIFT. Since you have no design background, private colleges like IILM University will suit you the best and you can also look for Universities that conduct their own entrance examination. I have listed down some options that will help you change your stream to Fashion and also pursue a postgraduate course in the same.

• M.Ftech(master of fashion technology): For this, you need to have a BE/Btech degree or undergraduate degree from NIFT or NID.
• M.Des (Master of Design): For this, you are supposed to have a diploma in design(from NIFT or NID) or any other undergraduate degree. (12th+4 rule).
• CEED: This requires admission through GATE and is only for engineering designing. So if you are interested in apparel designing, this one is not for you

For other designing fields like interior designing and industrial designing, your BTech degree will be beneficial. Fashion Engineering is a highly sought-after profession these days. So don't hesitate to switch your stream and follow your profession.