I Was Vacationing In VA About 3 (beach) Weeks Ago

I was vacationing in VA about 3 (beach) weeks ago and I have now noticed a difference in my bowel habits. I go to the bathroom first thing in the morning and all is Ok and in about 1/2 hour I must go again (with cramping like you have the flu) and then I have a loose bowel movement. This does not happen every day. Should I be concerned about something serious?