You have lost 9.5 lbs. in 2.5 weeks? That is an insane amount of weight to lose in such a short time period, you should be so proud!!! Weight loss is not linear, there will be plenty of weeks where you will lose but also weeks that you stay the same or show a gain. This is a huge mind game and it gets so frustrating at times, but if you stay consistent and patient I promise that it pays off!
I am not sure how tall you are, but I agree with Carol that you might want to up your calories. I am 5'4 and weigh 171. I aim for a range of 1400-1650 per day and still lose on that.
I am sorry about your back, that can be miserable. I have had back issues that come and go but nothing like what you are dealing with
I have lost 85 lbs. since November 2016 and I have worked out very little in that time. Something I hope to change, but in my case it was changing the diet that made the biggest difference.