I have the same problem Lynn....
In my case it was two seperate conditions except one was influenced by the other. First of all I have IBS or irritable bowel syndrome which causes the cramps just like you are describing. When it gets bad I think I would rather shoot myself than deal with it sometimes.
The connection with the HRT is that your shots balance your hormone level. When you miss a dose suddenly your hormone levels shift radically which causes an emotional stress that is a trigger for the IBS. Hence the symptoms i.e. cramping, become much worse.
One thing I have noticed over the last month is that since I started taking an anti-anxiety medication for an unrelated condition my IBS has been virtually non existant. I thought it was coincidence until I went back and read the pharmacology print out that came with the medication again and sure enough one of the things that it's prescribed for is chronic IBS.
I don't know if your situation is the same but what you describe mimics my issues perfectly. You may consider seeing a gastroenterologist in addition to your primary care physician.
Now...as a disclaimer. I am not a physician nor do I play one on television. These are all my personal experiences and in no way are meant as a diagnosis or as attempt to provide any medical advice
