Salary Negotiation

I got a offer of 15 LPA,I am currently 7 years experience,TCS is offering 11 LPA ,My current ctc is 9 Lpa In my 7 years i have switched 4 companies

First 2 were customer service and 3rd one was a software from there i moved to tcs but got no hike from the starting day

The work is manageable and I am also having a health issue in my low back from 4 years which makes me do less work

Please suggest me what to do?