I would definitely call your OB, no matter how embarrassed/silly you may feel. I spent a small fortune on extra copays just for peace of mind :) My son was my 6th pregnancy (first one past 14wks) and I felt him at 16wks - I was told this was early, and also that the more pregnancies you have, the more likely to feel them much earlier. I also learned that feeling the baby has to do with where they've implanted (my son was way at the top) (some friends who's babies implanted near the bottom weren't felt until after 26wks). After feeling him for a week, he'd seemed to disappear for 3wks so they had me in to listen for the heartbeat - it took the OB just over 10mins, but the baby had hunkered down as far below and towards my back as possible, so that's why I'd stopped feeling him for a while.
Good luck!
P.S. I ended up having a high risk pregnancy and had to switch from my OB to AGH - they don't recommend the 3D/4D for many reasons, but mostly because you need a calm/still baby and mine was nicknamed "Spazz" by the docs, never being still for more than a second. So, just a warning that getting those u/s may not be a fit for your pregnancy.