Should I go to my doctor and get some tests done?

Okay so my period is 3 weeks late and normally I have super heavy with really bad cramps that even painkillers can't get rid of but this time there was no sign it was coming and I have no cramps, just really tired and want to sleep. My boyfriend thinks I should make an appointment and ask for a blood test or at least try to find out what's going on, but I'm just not sure. I don't like wasting time going to the doctor if nothing is wrong so what do you think?