After having a pulmonary function testing & spiro breathing test done, nothing showing obstruction. I'm constantly short of breathe. What's next step?

Short of breath. You need to have cardiac work up done.Shortness of breath can be due to some heart disease as well as pulmonary condition.You need a chest xray to rule out lung disease beside pft and spirometery, sometimes you need cat scan to rule out pulmonary embolism.And for heart you need an exam, ekg, echocardiogram and/or sress test to find the cause of your shortness pf breath.
Rule out other cause. I would also suggest that they rule out restrictive lung disease. This may be detected as well by pulmonary testing.