We started off about the same weight, and at month 4 (I just checked my spreadsheet), I'd lost 52 lbs, so not much more than you. It seems to be pretty common to lose about 10 lbs a month for the first few months (although some people have a big drop the first month (I did not), which is likely a lot of water weight - before settling in at a slower rate of loss). After the first six months or so, I dropped down to maybe five lbs a month - and after I passed the year mark, there were some months when I only lost about two lbs. It took me about two years to reach goal.
If you stick to your plan, the weight will come off, whether fast or slow. There are so many factors that influence your rate of loss - age, gender, body build, how muscular you are, your metabolic rate, how active you are, whether or not you lost weight before surgery, starting BMI, etc. The only things you really have any control over are how closely you stick to your food plan and how active you are, so if you do well with those two things, the weight WILL come off. I ended up losing over 200 lbs, so definitely don't lose hope!
P.S. of course, if your scale actually weighs differently than the one at the doctor's office, well then there's that, too...