Hi. Are you saying the lightheadedness is constant or does it just happen when you get up from a sitting or a lying down position?
And sorry but can you expand on the weird feeling you mentioned?
I don't think we can attribute this merely to stress
There are some other possibilities, though--anemia, low thyroid even though you're on levothyroxine, dehydration, and possibly cardiac as in an arrhythmia.
I can't give you just one specific diagnosis here but you should let your doctor know about this and I would get some blood work and an ECG
Let me know if you need to discuss this any further please