It's all about diet. Lots of protein and some carbs and fat. I can't stand all these no carbs at all diets... rubbish. Sure you will lose weight on many cos you are not eating properly. Your body doesn't actually know the difference between carbs, protein etc etc. It is all about nutrients. The key is calories too. Many people think there is a fat gene but it doesn't really exist (sure some get bigger than others much easier). Inactive thyroids etc account for 1% of the population and even in that 1% it is not the reason for them having fat.
Just keep your protein high and keep on doing the cardio and ab work too. Make sure you do strenches before and after your workouts too. It goes on your stats etc. But the average man should be having about 2500 per day. So make sure you have about 2300. If that is not working try 2200 and so on. But don't go on crash diets. I have never calorie counted (would hate to) but I guess I have never wanted to slim down or get rid of fat somewhere. So you are best just having a plan of things you can eat. So not a schduele cos that will just demotivate. Just have an outline of what you can have for dinner (many different meals) and just pick one each day. Do the same for other meals and you should be cool.
The are many products you can take to help you out. You can get them in many sports/vitamin outlets. Or you could go down the route of gear and other not allowed compounds.
I would pick clen if you had to have one. Cos you don't want to cycle do you? You just want one substance so you couldn't be doing winny alone or primo or tren etc. I hope it goes well for you.