HCG levels insight/help please

Ladies I took a digital on Wednesday and got a positive result, I was 6 days late(or so I thought). I miscarried in April so dr wants to monitor my levels. Wed hcg was 53 and today was 154. So levels have tripled. My mind is reeling bc my Dr hasn't called me back to discuss results or anything. So questions...

Am I not as far along as I thought? Last period was 6/22-24. Maybe I ovulated or implanted late?

Also, moms of multiples, does tripling of hcg in 48 hours usually mean multiples? Twins run in my family so I'm super curious! ❤️❤️❤️