My first real scare

Less than a week ago, I felt an odd pain in my lower abdomen - to the left side of my uterus.  There have been many odd pains and twinges all through this pregnancy, but this one jolted me like a lightning bolt.  I had been in the pool, and immediately got out of the water, headed upstairs and called the doc's office.  The nurse was very kind, saying that it was probably nothing but since I had worked so hard to get that baby in there, why don't we come in get some reassurance from a doctor.
After a quick visit and ultrasound (surprise opportunity to see the little bub dancing around inside me), I was assured that everything was okay, and sent for a more detailed U/S a few days later.  Again, everything was declared just fine, and the pain had not really recurred in such strength so I began to relax and think it all a crazy over-reaction.

Then, just last night, the worst of the pain began - lightning bolts to that one spot coming in constant waves.  It built to pitch, catching me mid-speech and winding me completely.  The pain lasted about 10 minutes, sometimes decreasing enough for me to walk home with my hubby and express what was happening, and other times building up so strong that all I could was grab his arm and breath.

We made it home, I got into bed, and slowly the pain disappeared.  There was no blood.  I said a quick prayer of relief and gratefulness to my little one for staying with me.  I called the on-call doc and was told to take Tylenol and call back if the pain increased again or there was bleeding (not reassuring).  Then I grabbed hubby's hand and cried for a bit, while I took in what had just happened, and how frightened I really was.
For a moment I thought about what I would do if I actually had ____ (I can't even write the words), and I wanted to die.  Just the thought of it hurt too much to think about, and I quickly pushed it out my head.

This pregnancy has always seemed tenuous, miraculous and overly-precious.  I feel wrong and cruel thinking that somehow it is more so than the pregnancy of someone who isn't infertile and can just just get pregnant again, but I can't stop the thoughts from coming.
 I worry that my baby isn't as strong as theirs or as "natural"...that somehow all the fertility drugs and medicines will affect him/her in ways we don't even know about yet.  I worry he/she will also be infertile, and have to go through the same pain and disappointment when they are ready to start their own family.  
DH says I like to worry.  I think this is a silly comment.  No one likes to worry...I just can't help it.  This is my baby, my life, my heart.  I love him/her so much already, and all I care about is keeping him safe and happy, warm and loved.  Hmm...I think I'm beginning to understand my mother more.

FOLLOW UP TO POST:
After researching some forums (thank you Google), and talking to the doc, the consensus is that it is probably just good old round ligament pain (RLP).  I had no idea that RLP could be so intense, but I read many comments from women online who thought they were having contractions with RLP and were also completely doubled over from the pain.  I also saw my own description of "lightning bolts of pain," which made me feel even more sure that I was experiencing the same thing they had experienced.
I'm completely relieved, though not excited that this pain will probably recur throughout the pregnancy.  Ah well, at least now I will be prepared for it.