Worryingly short/light/almost non-existant period - why?

[Jacksmybaby]

Have been on fluoxetine for 4 weeks, for PMS/PND. Normally periods are: 2 days very light/irregular bleeding / more brownish red mucus than blood (sorry TMI), followed by 5ish days proper bleeding. 4 days ago started my first period after going on the fluoxetine, had the first 2 days of light bleeding, then NOTHING. Have done pg test today in a panic but has come up negative. Any thoughts on what this could be?

a lot of ADs have quite an effect on your cycle/hormones, but if you are worried then you should speak to your gp. iirc when i was on sertraline my cycle was a bit off for a month or two.

Thanks. Good to know at least it's possible there is another explanation other than pregnancy!