welcome to Healthcare Magic.
If your symptoms like light headed and and swimming sensation are occuring after stoppage of citalopram
then it is related to withdrawal symptoms
of citalopram due to abrupt discontinuation of medicine. So, restart your treatment.
Same time these symptoms can occur due to part of PTSD
symptoms, low BP
and vitamins deficiency, which need to rule out in your case after evaluation, and treatment according to cause.
Wish you all the best.
Dr Ashish Kumar Mittal