Exersicing & eating healthy but

It sounds to me like your calorie counting might be off. Are you weighing everything? Trusting calorie counts from restaurant portions? Logging every single bite that crosses your lips? Including hidden calories from food preparation? If you don't have one, I would recommend getting a digital scale and going back-to-basics on logging. Include everything for 2 weeks minimum- even weigh all your fruit and vegetable portions. If you eat peanut butter, tare the spoon and weigh it. If you drink coffee, tare the scale with the full cup and weigh the creamer in fluid ounces that you add. Seemingly minor eyeball measurements can really add up.

This right here.

You are most likely eating more than you think. Log everything! Even just a 'taste' of this or that. I log everything, including gum. I weigh/measure my food. If I'm still unsure about something, I go with the higher calorie count as opposed to the lower. You cannot continually gain on a calorie deficit unless there is something medically wrong with you.

You might want to get your thyroid checked. I gained 20 pounds in 6 months. I finally went to the doctor and my blood work indicated my thyroid was not working properly. I am now on medication and struggling to get this weight off.

OP, you actually can maintain your scale weight while losing body fat and gaining muscle. Check it out:

http://www.nerdfitness.com/blog/2011/07/21/meet-staci-your-new-powerlifting-super-hero/

Go to the dr. and have them check your blood sugar levels. Same thing happened to me last fall, found out my blood sugar levels were incredibly low...I was exercising, watching my food intake and working with a personal trainer. Even my trainer was like there's something wrong, no way I could be gaining weight and inches. Turns out, while I was eating the right amount of calories, I wasn't eating balanced, and my body was counter-acting all the hard work I was trying to accomplish. Once I started to eat a heavier breakfast and less at dinner it made a difference. Now I"m seeing loss, but it's not overnight like I had hoped. I'm working hard for it! Good luck, hope you figure it out.

When you exercise, wo you use HRM. If not, you might be grossly underestimating.

And besides, you may not have a lot to lose, like me, im 53kg going 50, at 5ft 3. and I am much older than you, metabolism will be only half of yours probably. Trying to lose these last 3 kgs, and it's been stuck for like ages, already dropped 2 kg from 55. and now, it's finally coming off, ever so slowly, like 0.2-0.3 kg per week. I did a few changes.

1. Keep a deficit of 250 or so almost everyday. There will be a day or 2 when I'm hungry, I will go over a little but not to go over too much. Exercise 6-7 days a week
2, did nike training club doing mainly toning and increase strength circuits 30-45 mins
3, after NTC, cardio for 30 mins
4, alternate days, elliptical with resistance followed by abs and core exercises from nike training club, and add some skipping.
5. Heart rate - try to heat 80% for 30 s to 1 min every other 10 mins or so. For NTC circuits, you will get that throughout the circuit.
6, eat 20-25% protein, try to go lean, eat more fish, avoid white carbs (white rice, bread) at night.
7. Add yoga 15-45 mins, whenever I can. Walk whenever I can after lunch.
8. Once a week, run at least 5km targeting 10 km.

Without seeing your diary, and not knowing the intensity of your exercises, kinda difficult to comment what right or wrong.