Have disconfort in upper abdomen, light headedness, lot of gas. Blood test this friday for ulcer. Is this serious condition?

It depends,,,, It depends on if you've got an ulcer or not, but it doesn't seem likely you've got one as you've got discomfort and gas and an ulcer would likely be much more painful. But you'll not know unless you get your test so go get it and see what it is. Good luck.