Any Idea... I'm at a loss?

Kami
Hi All, 
This is my first time posting, but I'm constantly on here reading everyone's posts, taking heed of the advice and encouragement given during the highs and lows.
Now I'm stuck and can't find a story like mine, so here I am writing my first post. 
Last August I found out I was pregnant with twins, sadly one was in my tube and the other in my womb. I had to go for surgery and lost my tube, the stress of the operation also caused me to miscarry the other baby.
Since then we have been ttc, March this year I miscarried again. 
I have always had a cycle of 25-28 days never longer. I have been charting my BBT and taking my vitamins. My period has always been very heavy and very painful lasting 5-7 days. 
This cycle has really confused me... 
My ovulation sticks say I ovulated and we BD 'd around those dates and leading up to it. 
13dpo I spotted only when wiping
14 dpo bled no as heavy as usual and light cramping
15-17dpo spotting when wiping
All tests have been BFN's!!!! I've been extremely tired (having to take a naps), nausea , boobs tingle now and then, body aches and terrible bloating!! But my bbt has dropped so surely if I was pregnant it was stay high. Oh and at 5am everyday I wake up , check the time get annoyed with myself and go back to sleep until my alarm.
Has anyone else experienced this? Did I just have a 1day period? Or could I be pregnant?  
I've attached my chart for the bbt charters to maybe help shed some light if they've experienced this. 
Thanks in advance 😊 xxx