Lower abdominal cramps at 17 weeks??

Hello all! I'm 17 weeks 4 days currently. Today I've gone for a walk to get some groceries and I carried a big bag of navel oranges and milk back home. Ever since I came home I feel cramps all over my lower abdomen. Should I be worried? Is it ok to carry weights? I usually carry weights regularly like groceries always. Should I stop lifting weights like this??? Please advice!