Can which affect it...medication or anxiety?
SSRI's, no...I don't believe so...
Anxiety? Definitely. I had a amenorrhea for the better part of 3 years when my anxiety was at its worst. (compounded by weight loss, but yeah...anxiety induced loss of menses.)
However, if it is possible you may be pregnant, make an appointment a.s.a.p with your OBGYN.
S.C.