During meditation many thoughts are coming in my mind. I try to concentrate on breath, but I did not know if i concentrated on breath or not. After completing meditation i feel sleepy. Is it correct or not? Please send me correct solution.
Yes, during meditation thoughts easily come up in the mind. It even happens to advanced meditators, as you can see in Autobiography of a Yogi, chapter "An Experience in Cosmic Consciousness." We all try our best to re-focus the mind again and again, whenever it wanders.
However, if you don’t know if you concentrated on your breath or not... that means that you weren’t actively concentrated. Also the fact that you feel sleepy after meditations makes me think that you tend to shift into a subconscious state.
A solution for you might be to meditate only for a short time, emphasizing quality: do it with all your concentration, with high energy, with inner interest. Quality is more important than quantity. In meditation, try to be as energetic as you are when you do some active work outwardly, just taking this energy into the inner activity of meditation.
Energize vigorously before meditation. Enter into meditation full of vigor.
You might also find it helpful to meditate with half-open eyes.
Affirm with power with Yogananda: "I fight for Thee in the temple of meditation."
Try that and you might find that you feel very awake when you end your meditation. And you will know very well that you have been concentrating on the breath.
Once you have these effects, make your meditations longer, a little at a time.
God bless you, jayadev