anyone have Hcg levels not double and baby be viable????

Carol
My Hcg levels are not doubling and we only saw a gestational sac...I'm around 6 weeks give or take....levels are going up but couldn't see yolk Sav even.....
11,971 on the 3
15,833 on the 5
22,011 on the 7.
Any advice please. Next scan is t till Monday the 17th.