Hi
I was in a similar situation, came off all contraceptives and started low dose HRT. I think it was around 18 months later....a period! Had all the pre stuff, boobs, cramps etc but because they had said I was post from blood tests all hell let lose! After all the tests it was completely normal but lots of worry for me! I was around 50ish at the time.
So, don't be surprised that once you've got one lot of stuff out your system after a while things might have their last fling!