I'm due in 6 days I'm 8dpo when should I test

Jemma • Been trying since last year had a miscarriage in December :( but trying to conceive again
I'm due on 31st I'm 8dpo when should I test I'm getting heartburn period like cramps but not as bad,back pain,feel sick,going wee more don't wana get my hopes up incase when should I test