What causes dizzy spells?

For the past 2 days i have been extremely dizzy every time i stand up lay down roll over or sit up even looking upwards is causing me to see a blur and i feel really faint. I do eat though atm not alot and have been very stressed through a seperation with my husband and have been drinking alcohol nightly and also smoking cigarrettes I dont know if any of this is a cause or if its blood pressue or? What is this and what can i do to fix it? Thank you any answer would be much appreciated.