I have av 100 degree fever 24 hours after having an HSG test to see if my fallopian tubes were blocked. Is this something to be concerned about?

Maybe. It is not unusual to have a slight fever in response to a procedure. But it can be a sign of infection. If you have cramping, bleeding or the fever gets any higher, you should be seen. No matter what, you should let your doctor know what is going on. Good luck!