Rightfully concerned or paranoia?

I have my appointment for the 'big' ultrasound this week & I'm so anxious. I'm 19 weeks along in this pregnancy & I think that I should have felt some definitive movement by now. I've been thinking about it for the last 3 weeks or so. I get weekly e-mails about my pregnancy and there was a link about fetal movement, so since I've been concerned, I clicked it. There were multiple women that are pregnant with their second, third or fourth babies and were saying they had felt movement at 16 or 14 weeks. One said 11 weeks!!! Personally, I think she just had gas. Maybe I'm just shooting it down to make myself feel better.
At any rate, this last week or so, I've been trying what I know to feel any movement. Before going to bed, I've drank some orange juice & then laid down to try to feel anything for about 45 minutes. I've tried laying on my belly, with my hands underneath to detect anything. One afternoon, after sugaring myself up & laying down, I think I may have felt something, but I'm not sure (it's my 4th, shouldn't I know by now?). I keep telling myself that I'm not feeling anything, because I've been too busy to pay attention. I'm trying not to worry about it too much, because if something did happen, I can't do anything anyway. But, of course, I'm concerned.
Has anyone else felt this way? I don't want to be paranoid about nothing, but I can hardly wait to hear the heartbeat. I would really like one of those little devices to hear the baby's heartbeat right now. Until my appointment, I'll just hope that this is a healthy, mellow baby.