CD35 and negative everything.

Evin • Momma of twin🌈 babies.
Hi Ladies! 
Today marks CD 35 and still no period.
I'm ALWAYS between a 25-29 day cycle. 
The last time I missed my period, like this, I was, in fact, pregnant. And like now, the HPTs were negative until about week 6.
Unfortunately, that pregnancy ended at week 11. 
I've got all of the pregnancy symptoms going on. Acne, tired, super emotional (I started crying while on the phone with our internet provider lol!), and nausea waves.
Today, I got a blood test which was negative, as well.
Has anyone had a successful pregnancy but had undetectable HCG
I'm so confused at what is happening in my body.