periods?

hi Ive already posted this,but think twas in wrong place sorry.
Ive been on Citalopram 10mg for about 4-6months.Im 39 years old and my periods are usually regular,Ive not had my last 2 periods just a slight pain around my due time which I usually get just before I start.Could this be a side effect?has anyone else had this?Also Im currently having other health problems which Im stressing and obsessing about,could this have caused lack of periods?Theres no chance I could be pregnant,has anyone else had period problems on citalopram?
Thanks
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