I Have Been Having Stomach Problems ,just Not Feeling Good

I have been having stomach problems ,just not feeling good like upset stomach for months, no serious pains doesnt matter what I eat always feel sick to mt stomach my temp is running 96.1 and 96.5 I have been having constipation little tiny stools come out sometimes I strain ,then when I have coffee or salads, then my bowls will move . at times been light headed , have no energy , I have thyroid since I was young taking 200 synthroid brandname no generic , have had a upper GI 10 years ago had ulcers scheduled for another one in a month dont know if I can wait that long , my Dr retired and need a good one I feel like a mess , also have a colonoscopy scheduled , but dont have good sucess with intaking the medicine for the test I throw it up help