Viability of multiple pregnancy

Patient: I am 6 weeks pregnant and and since my first blood test I have had a feeling that I was having twins. I did a pregnancy test at around 3 weeks, and even though I had not yet missed a period and it was in the evening, the test showed positive almost immediately. My HCG levels were much higher than average when checked at 4 weeks. I am ‘showing’ already. And strangely enough without mentioning this a few people have had ‘hunches’ that it is twins.Upon re-searching more online, i learned that after the age of 30 chances of having twins increase and that if you have one or more children and if you have had 4 previous pregnancies it also increases chances of conceiving multiples. I am 34 with a 9 year old daughter and this is my fifth pregnancy. I unfortunately did not carry any beyond 8 weeks.Today we went for a ultrasound as I was experiencing some light spotting and cramping on my left hand side. The ultrasound showed two sacs. One with a fetus and heartbeat  of 121bpm and the other sac was more difficult to see, slightly smaller with no obvious fetus and no heartbeat, but there was a darker area in the sac that was pulsing (like blood flow.)My gynecologist sees a slight bleed and based on my history and risk of miscarrying, has recommended bed rest and has prescribed oral progesterone and a mild aspirin. I am to go back late next week for another ultrasound.Could the second sac be a viable pregnancy, but just slightly behind the first?I really don’t want to get my hopes up, but would love twins.What do you think my chances are of seeing two healthy little heartbeats at our next visit?