Hello Sundeep,

Let me tell you something. You're not the first person who has left the BTech course and joined some other course. The gap of 2 years seems big now but in the long run it doesn't matter much. 

People have completed engineering and are sitting idly at home in the name of preparation. There are people who fail at 10+2 level and pass after 2 to 3 attempts. If you did bcom and studied sincerely in those three years, you can have a wonderful career in commerce field. You will be asked why did you leave engineering or what did you do in these two years?. But you can answer telling them the reason why you left engineering and you chose bcom. 

There are students who prepare for engineering and have a gap of 2 to 3 years after 10+2. Medical students even drop for 3-4 years to pursue medical. Aren't they succsssucc in life ? . 

The gap in your career isn't big if you're able to justify it . For now study the bcom course sincerely and then you can join MCom or MBA later and you can make it big in life. It all depends upon your hard work, sincerity and dedication. 

All the best.