Try meditating. Dont try to stop the thoughts. The more you resist them they ll persist. Just let them come n go, you need to practose this. But dont act on them, its like background noise, its there and you let it come n pass. Its like you are waiting on a bus stand,there is noise of the traffic, cars honking, people talking everything is just there and you let it pass. Without attemoting to stop the noise neither paying attention to each n everything. It is tough but practise it. Meanwhile, get in touch with a psychologist. S/he will gelp you explore th source of sleeplessness.