For About A Month, I Have Had Nausea. Then,I Vomited

For about a month, I have had nausea. Then,I vomited one night and went to the dr. Because I was having diarrhea for 3 days. He diagnosed me with ins. And gave me medication,which has stopped the diarrhea,but I'm still feeling a little weak. I am 71 yrs. old. A female. Always been in good health,except had my gallbladder removed about ten years ago. I'm scheduled for a consult for colonoscopy later this month. I'm nervous about the whole thing...