6 dpo, 8 days til AF.. when should I test??

Hey guys! My cycle has been somewhat irregular since I had my first child 2 years ago. I go between 27 to 31 days per cycle, and it's very annoying!! Lol I've been tracking using apps etc but we've been ttc for almost a year now with no luck. It's getting very frustrating! Even harder is knowing when to test, I'm 6 dpo now and according to all my apps AF should be here in 7 or 8 days.. 6 dpo doesn't even seem long enough, although some tests say you can test a week before AF is due. The whole thing is getting very frustrating, anyone with me!!!???