The thing I've learned from meditation so far: Don't try to be clever, just follow the instructions!
Anapanasati (meditation on the breath) works just the way it should be. It was highly recommended by the Buddha himself and successfully used for the last ~2500 years now. It's really simple: When you breath out, know you breath out.
If you want to develop samadhi (concentration is a misleading term, let's just call it peaceful stillness), then the best way is to choose an mediation object (breath, metta, walking, ...) and follow the instructions.
In this case I was not noticing my breath but was noticing my thoughts I did it by asking "what's the next thought " and tried to observe my thoughts mindfully
Don't do this. You will eventually get caught up in thinking and emotions. In meditation (samatha) thoughts are a distraction. They pull you away from your object of meditation. So dropping your meditation object will pretty much end your meditation.
Dealing with distracting thoughts
I guess half of all questions in this SE relate to that topic, so I'm just gonna link some instructions. In general, you have to find out by trying what works and what doesn't. What makes you (your breath) more peaceful and what makes it more stressful.
https://www.youtube.com/playlist?list=PL603BD0B03E12F5A1 (you probably heard this)
And it seems it is easier to do this type of mindfulness when in an environment with a lot of distraction . (Walking or running etc.)
I myself noticed that in such a environment it's very beneficial to 'sort' those distraction in regards to the six senses. This is seeing, hearing, thinking, tasting, feeling, smelling.