Hi, Lori. An infection can cause cramping and contractions and/or preterm labor, so I'm glad to hear you aren't having any other symptoms.
I know what you mean about not knowing when to call the doctor or go to L&D. I had a lot of anxiety about that too. There were two things that really helped me. First, our childbirth preparedness instructor (who I got to know very well with all my trips to L&D for both kiddos) said that the time to call is when anything changes. A change in discharge; a change in the pain level of the cramps; cramps changing into contractions; or the frequency of the cramps/contractions increasing. Also, any new feelings count as change, like feelings of pressure "down there" or pain in your thighs. Or nausea.
The other thing that helped was to print out the list of preterm labor symptoms and put it on the fridge. Any time I though something was up, I'd head to the kitchen to load up on water and read through the checklist. If I started saying yes, I knew it was time to call the doc again. It made the decision-making process very black-and-white when I could focus on the checklist and not on my fears and emotions. Keep us posted...
Angela