Vanishing Twin

Went today for my first ultrasound and was not very surprised (been having a feeling) that it was twins. One twin is no longer viable and based on measurements it was within the last couple days that it passed. Both were measuring 8 weeks 6 days. The non viable twin should absorb into my body. Now I'm just worried that the other one might not make it either. Have another ultrasound scheduled in two weeks to check on the remaining twin and make sure the other starts shrinking. Trying not to be worried but it's a little hard.