I'm sorry for your loss.  What you're experiencing sounds like panic attacks to me.  When I experience them my heart races and I get a sense of the flight or fight feeling.  I have dealt with panic attacks for about 13 years now.  They started when I was 14.  At that time I did relaxation therapy with a psychiatrist.  That helped, but ended up taking Paxil for about a year.  That did the trick (I think the combination of therapy and medicine worked for me).  I also tried accupunture, which was relaxing, but I don't think it was for me.  (It might be something for you to try?)  I was relatively panic free for many years.  I would have minor attacks when I was under stress or more importantly sleep deprived.  In 2007 I had my daughter and in June of this year I had my son.  After each of the births the panic attacks returned.  (Due to loss of sleep and crazy hormone changes.)  With my daughter I took Zoloft for 6 months, which helped.  I was told by my midwife to take fish oil, which might help you.  The one thing through all my experience with panic attacks that has helped the most is talking to someone about it.  If you have someone who is understanding and will let you call them during the middle of the night when you sense the panic attacks coming on should help.  My brother lost his best friend last year and has been dealing with middle of the night panic attacks.  I am his go-to person.  We will stay up and talk for a half hour to an hour telling stories about is friend, then we talk about things that are coming up in both of our lives.  There may be a group in your area that you could join, too?