Your symptoms are suggestive of High Altitutude sickness though it genarally occurs at an altitude beyound 8000 ft. It is generally seen in mountaineers. It happens because of low oxygen
in the air. It is advisable that you don`t halt at high altitude and in case of situations mentioned by you, climb down to a lower altitude and spend night there. You should take plenty of water, have regular meals and avoid alcohol. You may carry portable oxygen cylinder which are available in the market for sale and for rental as well.