Can anyone suggest a medication that worked for them who tried Prozac and Lexapro?
I see from what you've posted elsewhere that your doctor thinks the lightheadedness is cause by anxiety/stress which is why you've been prescribed first Prozac and more recently Lexapro, but neither have solved the problem. You also write that you've only been on Lexapro for 6 weeks and during that time you've gone from 5mg to the maximum 30mg.
The fact that Prozac didn't work tells us very little. No antidepressant works for everyone. If it did we'd only have one. Secondly, it takes 3-12 weeks for an antidepressant to kick in so the lack of response from Lexapro also tells us little, plus the quick escalation in dose right to the maximum could itself be causing lightheadedness.
You also ask if stress could be responsible for this and whether stress can last 6 months. The answer is yes to both. However, it would be unusual for lightheadedness to be the only symptom, though you do mention neck tension.
I suggest there is a relatively quick and easy way to test the anxiety hypothesis, take a benzodiazepine daily for 4-5 days. I suggest 5mg of diazepam (Valium) starting with half a tablet at night for 3 days and going up to the full tablet only if the half dose makes no difference. If it works then it would indicate the symptom is anxiety/stress related though it isn't conclusive as benzodiazepines have wider effects in the brain so could be correcting a brain anomaly that's been missed. However, this is probably a long shot and anxiety is the far more likely explanation.
However, benzodiazepines are not the ideal long-term solution so if the diazepam demonstrates an anxiety cause then antidepressants are still your best med option. You'd need to give the Lexapro more time to prove itself. If it doesn't then a med from another antidepressant class should be considered, either a SNRI (though not Effexor (venlafaxine) which is only another SSRI at typical anxiety doses), or one of the less serotonergic tricyclics, amitriptyline, desipramine, or nortriptyline.
Just a couple of other random thoughts. You're on a BP med, when did you start taking it? Are you on any other meds, and when did you begin taking them? Did anything significant happen around the time this first started, or in the 6-9 months before that?