Late period

My last period was April 9-12 cycle usually last between 27-28 days well here i am on 31 day of cycle(May 9). was suppose to get my period on may 5-6 was sick last week had a alot of lower belly pain (thought maybe i was constipated), couldn't eat without feeling light headed nd nausea,felt really sluggish.....now my back hurt really bad and I'm cramping but not like period cramps......should i test or continue to wait on period?

May10- negative pregnancy test