Update  

Since I was discharged from the hospital I was battling a full-blown postpartum depression (never had anything like this before). Anxiety attacks were the hardest part complete with chest pains and vomiting. After about two weeks on advice of adgal I managed to identify the triggers: I think going home while leaving twins behind in NICU was making me sick. It was hard not being there for all the day and night feedings.   I am basically back to normal now. Having Margot at home helped and William will be discharged tomorrow after a 20 day stay. I still need to restore my relationship with Anna after a 6 weeks hospital stay. Physically I feel OK although prolonged bedrest did bring my activity level way down; I am getting back to normal slowly...  
In the end, Margot spent 10 days in NICU and William 20.  Margot had very minor issues: one apnea episode and too sleepy to eat.  William had beathing issues, minor apnea, eating issues (could not suck, swallow and breathe at the same time and he still can't) and tachycardia (rapid heartbeat).  He will be discharged tomorrow with a beta blocker that he will be taking for a few month; cardiologist told me he will outgrow it by 1 year or sooner.  
Overall, both twins should be OK and I am very grateful for that.