Getting past a weight-loss plateau?

Someone may have suggested this somewhere but I haven't had a chance to read through all the post so I apologize. I had the same problem around my 68ish pound lost. I was typically losing 3 lbs a week and it came to a screeching halt all of the sudden. I started searching for the reason. The first thing I found out was I actually was not eating enough. And my after I purchased a heart rate monitor I found out that I was burning way more calories that what myfitnesspal was telling me I was burning. According to MFP I was burning 340ish when in reality it was closer to 550. I talked to one of the very nice trainers at the gym and she told me to increase my intensity of my work out. So I started researching ways to increase the intensity. I stumbled upon high intensity interval training. So 2 weeks ago i started working using HIIT. I warm up to my target heart rate of 150 for 3 mins on the elliptical and then I go balls to the wall for a minute then I recover for 2 mins then balls to the wall for 1 min and alternate for 30 mins. http://www.shape.com/fitness/workouts/8-benefits-high-intensity-interval-training-hiit

A) You need to change up your workout. Shock your body. You'd be surprised how quickly your body can get used to a workout routine. Once your body get's used to it, it doesn't have to work as hard which results in fewer calories burned. You should switch up your workout routine every 3-4 workouts. Keep that body guessing!

You could be gaining muscle. Are you sure that your not losing? The numbers on the scale are only the half of it. If your gaining muscle, then that will show on the scale as well; either as a gain or as a zero. Meaning you didn't lose or gain.

The best way to target your problem is to change up what isn't working. Your workouts, your diet, etc. And be sure to take your measurements as well, if you aren't already. You may be losing inches and not pounds(due to the strength training)

Good Luck!