I'd do a pregnancy test.
Disturbance in menstrual cycle isn't unusual when starting or increasing meds. The whole endocrine system has to rebalance. We all react differently, so it's impossible to say if you will skip or just be a little late.
You mention your age. Could you be in perimenopause? My cycle was like yours...regular as rain...until about 10 years before menopause, when it started to vary.
Thanks for the info. No need for a pregnancy test....I had that friendly visitor this morning! I did find information after I posted this that the brand I have been on can cause menstural cycle problems but normally shortened time and delayed.
I am 41 almost 42. The women in my family on both sides haven't had menopause or perimenopause at all before 50 but you are right, it is a chance!
Thanks for the reply.