Should I buy a test ??

Harleigh • Me and kyle had a baby in Dec 2013 he has aneselphaly and a missing bone in his left four arm. It`s been almost 10 month but I been off birth control for 8 months now.been trying again.and nothing yet
Went to the er on the 15th. Cause I feel out in the shower . They did a pregnancy test and it was negative. I was supposed to start my period on the 18th to the 24th my last day of , today and I still havnt started should I buy a test or wait a little bit?