I feel weak and feel like im going to faint any second. Dizzy and unbalanced. what to do?

normally if i smok i know im going to have gastric problems, but this time while i was traveling i had this weired experience of almost fainting and vomiting. i was taking pills for tiredness and travel sickness. it was like two weeks ago and ever since i have that weired feeling. i feel dizzy, unbalance and feels like im going to vomit any second or most of the time faint.. can't eat properly because of gastric problems perhaps, but im trying to drink a lot of water... im starting to worry now as i feel really weak and lifeless..