My Hcg levels fell and now are slowly rising, why?

I found out last Friday that i was pregnant but an Hcg level of just 19 obviously started alarm bells ringing. A test on Tuesday showed that they had fallen to 6 and i started to bleed last night, with no abnormal pain. This morning my Hcg came back at 10, i realise that this pregnancy is no longer viable but am worried about the reason why they are rising especially as i'm going abroad on Sunday. The nurse say's i've to come back tomorrow, as i will be away be Monday, to be retested. But i'm worried that something more sinister is going on and i'll be stranded abroad having an ectopic pregnancy or something. Any ideas what could be causing it?