Cannot drop weight

Patient: Hi, I was diagnosed with hypothyroidism in Nov. 2013. I am taking sinthroid every day. I eat a very clean and healthy diet. I do not eat fast food, soda etc. I drink about a gallon of water a day. My typical diet every day is a egg white wrap and coffee for breakfast. Tuna and a apple for lunch. Fish or chicken with vegetable for dinner. Snacks are usually carrots, celery, broccoli with hummus. Apple with a handful of almonds. My question is that I thought when my thyroid was back in normal range I would start losing weight. I exercise 5 days a week. Cardio, weights approx. 400 calories burned on those days and 10,000 plus steps a day. I am so frustrated with the fact that my weight staggers between 157-160. I am 51 and I understand It is harder to lose weight, but with the diet and exercise I do, I just don’t understand. Any suggestions would be appreciated.