Dear Meg: Wow, living in Italy. I envy you as I love Italy. But I'm sorry that you are having these GYN issues with a 16 month old, having recently moved.
The most common reason for a menstrual pattern like you have described is not having an ovulation every month. In a normal cycle, estrogen is produced all month. Estrogen is responsible for building up the lining of your uterus so you have something to shed each month. The good news is that you have enough estrogen to make a lining that does shed.
In a normal cycle, progesterone production increases following ovulation and release of an egg.. Progesterone "stabilizes" the uterine lining in preparation for a possible implantation of a new pregnancy. If you are not pregnant that month the levels of estrogen and progesterone fall, triggering the release of the uterine lining—your period.
So, if you do not ovulate, the estrogen build up of the lining continues, but without the usual ovulation associated progesterone. Thus, the hormone levels don't decline, and the lining stays up inside the uterus—as a missed/late period.
Alternatively, the built up lining can begin to shed on its own creating erratic bleeding patterns which are usually "too-light" or super heavy and prolonged.
As you may have read, causes for not ovulating are many: low thyroid (ruled out in your case), pituitary problems, ovarian cysts, physical stressors (eg sudden increases in exercise, crash dieting), emotional stressors (problems with partners/family, money), increased body weight, anorexia, rotating shifts at work, etc. In your specific case there are several possible culprits: recently stopping regular birth control pills, and moving to a different country. You also have a known history of irregular ovulations.
Yes, bilateral breast tenderness can be a very early sign of pregnancy, appearing as early as two weeks after conception. This is thought to be related to increasing levels of hormones such as estrogen. In a month without an ovulation, not only can a menstrual period be missed, but there can be breast tenderness as well. This is similar to the increased breast tenderness experienced by some women when first taking postmenopausal hormone therapy.
I would urge you to establish care with a GYN by getting another pregnancy test done just to definitely rule out an undetected pregnancy. That way, if you do develop prolonged or heavy bleeding you have a place to receive care. I would hope that your cycles reset themselves naturally. Your daughter's birth confirms that you do ovulate--even if it is not always super predictable.
Yours,
Jane