I've experienced it and its very disconcerting. I'm also a heart worrier and recently lost a lot of weight, for last several weeks was feeling very anxious and lightheaded. Called doc who said that my doseage of blood pressure medication now may be too much since I've lost the weight so he told me to take half of what I had been taking. Within 48 hours my anxiety went away and no more lightheaded feelings.
If you're on BP meds, check with your doc - they may need to be adjusted - even if your weight is stable, sometimes the body just gets used to the med after time