hcg too high??

hi there i was just wanted to see what you guys thought... my wife and i went to the baby doc on 4/16, we only saw sac and he was worried bout the little area on top left of sac,and the sac larger then what it should be, turning into a miscarriage? he asked my wife the symptoms she is having, and she told him then he said he's not worried bout a m/c.. he thinks it could be twins, he thinks this gray area could be another baby on top.. he had us do blood work that day and on sunday 4/18. we talked to him monday and he said her hcg was 90,000 (and she is only 6 weeks pregnant at this time), and he said 4/16 hcg was bout the same,and that he just think there are twins in there. so he made us go back for snother on 4/20, and it went from 90,000 to 115,000. so my question is are these hcg too high for only being 6 weeks along? could they be twins or more? just need some answers!!!