Hello, I've Been Feeling Sudden Dizziness, Inability To Eat, Weakness,

Hello, I've been feeling sudden dizziness, inability to eat, weakness, and stomach issues, like feeling full after only a small amount. I went to the doctor and they said it was from "not eating well or enough" and stomach acids caused me to feel nauseous/unable to eat, and it backed up my stomach. I was prescribed an acid reducing medicine, plus a stool softener and another medication only to be taken when I feel nauseous. I was told to only take it for three days and it sort of helped, in that time I was only allowed to eat four small meals, of anything between toast, rice, applesauce, and bananas. I started to slowly feel a little better than before but yesterday I was suddenly overcome with dizziness at work. I was worried it might even be pregnancy but I took two tests that came out negative, spaced two weeks apart. I've always had irregular periods but I still haven't gotten it. I'm hoping it isn't anything super serious.. Thank you for your time