TThat means I have to make choice Either continue b. Com OrLlb for 5 years Right? 

Yes. You will have two options you can go for 5 year law through clat next year. And then you'll have to start fron 1st year.
But if you complete your bcom. Then you can go for 3 year LLB after completion of Bcom. Clat does not offer 3 year LLB courses. So you can go for other entrance like Du LLb, MhCET etc.

If you want to be a lawyer then you can pursue llb after bcom which is for then 3 years. In total it will take you 6 years to have bcom and LLB degree. There are many colleges which provide integrated LLB course which is for 5 years which includes BA degree as well. So at the end it is going to take you 6 years

You have completed bcom 1st year and if you continue bcom and later pursue llb so it will take you 6 years in total

You are in 1st year of bcom and you switch to BA+ LLB    Course which is for 5 years then your 1 year of bcom won't be accounted and at the end it will take you 1+5 years to complete the course