Lisa - please don't freak out if you go to the early us and they can't find much. Amy and Emily both went early and at Amy's appointment, they even suggested that she take medication to induce a miscarriage because they were sure it was not viable! So, just make sure that you keep in mind that early ultrasounds are some times deceiving!!!
I know the lack of symptoms is soooo stressful. I remember praying every day for signs and symptoms to let me know that everything was OK. I would say that symptoms hit more around 6-7 weeks. I even joined a thread in the PAL section of girls that had NO symptoms and we were always nervous, but we all wound up with healthy beans! So, maybe you're just lucky!!
I have no idea about the tripling of the levels... could be twins??????????