I hate to burst your bubble here, I really do, but that's way too high to have been the baby at 12 weeks. At 3 months along the very top of your uterus is barely an inch above your pubic hairline. The spot in the picture, or any spot near your bellybutton at this point, is nearer the 4-5 month mark. You do grow faster with subsequent pregnancies, but it still looks much closer to where you'd expect to be at the 4 month mark. It's also too big to be baby, who is only 2 inches long and weighs less than a cd at this point (being the bones haven't begun to harden yet).
I get bumps that look similar and move when I push on them, too. It's more obvious now that I'm 12 weeks along, but I get them even when I'm not pregnant. Up there at this point it's most likely to be parts of your colon (in your picture, it's your descending colon) and you're just nudging a loop of it deeper in. It's still pretty cool, in my opinion. But I'm a nursing student, so a lot of what the body does fascinates me. The sheer complexity of what it does automatically, that our conscious minds would totally be unable to do even if that one task was ALL we had to do...it's amazing. I could go on all day.
Anyway, you should still be able to get close to where baby is. Lie down flat and put your fingers under your bellybutton and push down HARD. Like you can't see the tips of your fingers at all hard. (I'm 138 lbs right now and can see just the base of my thumb if I use that, that's how hard I'm talking about.) You'll feel a lot of squish, for lack of a better term. Then walk your fingers down until you stop feeling squish and start feeling firmness instead. That's where the top of your uterus is.
If you've got a doctor's appointment coming up soon, have her or him check your fundal height so you get a better idea of where you're at. It's pretty cool, if a little uncomfortable when they dig in. They should be checking your urine at every appointment, but make sure you have an empty bladder anyway. They'll be shoving at your small intestine down there and look, experience, okay? At least it wasn't much and my doc had just had her own second baby so it was more of an "I've been there" giggle than anything else.
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