Sorry did you take it orally LW44? It is probably because you are thinking about it that you are jittery? If you took it vaginally I'm pretty sure it wont have reached your head yet
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Try not to get too uptight about it, its so easy to worry so much about meds and meno that we can make ourselves feel worse with the tension. Things may feel different and maybe you do feel weird some of us do but remember you can't really do anything wrong and to be honest you cant do yourself any damage.
As Hurdity says not having a bleed after 6 months and it staying that way is much worse than doing something about making your lining thinner like it should be. I'm pretty sure you will be fine! but keep us posted!