What Causes Dizziness With Syncope And Breathlessness?

for a few years i have been getting dizzy spells where im to the point of nearly fainting.I will get really hot and start to panic and i find it difficult to breathe. I have been to the doctor and was told that my blood sugar levels might be low. I have tried glucose tablets but this doesnt seem to help.It always seems to be worse around the time of my period.