Bbt help! Please!

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I need help. By bbt has been all over the place this month. I got positive OPK on Cd 15 and CD 21 with negatives on all the days in the middle. As of today, I am Dpo 5. Normally I get a very triphasic chart that you can very clearly see two spikes in temp (one the day after ovulation and one about 6-7 days later). Those charts have always ended in BFN. Anyways, my chart is confusing me this month, can some one tell me what they think is going on? Thanks. Anything helps