I was surprised by mine all the time up until I went on Depo and got pregnant (yeah, I got pregnant after 8 months on Depo, following several years of being sexually active using primarily the withdrawal method and not getting pregnant...go figure...but that's another story).
After the pregnancy though I couldn't really be completely surprised anymore because my body and mood started doing a pretty difficult-to ignore monthly cycle...the 11-day warning was getting seriously depressed, the 9-day warning was my digestive system starting to act different, and the 6-day warning was an acne flare, which would clear on the same day I would finish bleeding (helpful, since it told me when I could stop using hygiene products). Then the cramps would start on the day before, and the bleeding would start within 3-4 hours of the cramps getting so bad I needed to take pain relievers. All extremely predictable, my body wouldn't let me forget (and the second time I was pregnant I knew a week before the pregnancy tests would detect it because the usual signs weren't materializing, so I was frantically testing every day).
I'm still getting to know my body on T. Haven't had any bleeding yet since the first one after the shot (oh please let that be permanent!) But I keep thinking I'm about to, because T's changed my digestive system function - the change is good, but it's basically stabilized me at the level of speed/regularity I used to only see in the week before my period. And I have occasional cramps/twinges in the reproductive parts reminiscent of the very first signals on the day before I started bleeding. But at least it's a constant feeling that I'm about to bleed rather than a constant feeling that I'm pregnant. And I expect the cramps/twinges will go away with time and atrophy of the parts.
