My girlfriend is afraid of my dick

Alright look this all started around a year and a few months ago when we started dating. She had an ex boyfriend that had a rather small dick around 4 inches hard and not too thick. She thought that most guys were around that size. The first time I got a measuring tape compare my 8 x 6 inch dick she audibly gasped and did an up down.
A few days later while we were watching a Disney movie, we were cuddling and I started sporting quite the erection. She moved her hand to it and was amazed not only by the size but by the girth as well.
We started having sex not too long after that and it was going great. I started introducing new positions and practices like bdsm. It was all going great till about 6 months ago when she started constantly turning down my advances, not wanting anything sexual done to her, she would act like touching me was a chore, etc. it has continued nonstop for the last 6 months.
She recently told me that her sex drive is very low compared to mine. She said that my sex drive was to much to keep up with so she just stopped. I got annoyed by all this prolonged abstinence and asked if it was me, if my dick was too big, if I was too sexual, etc. For the most part it was me but she was not going to admit it. She said I was way to sexual all the time and that my sex drive plus my large penis made it very intimidating to continue.
I just want to rearrange her guts why is that so much to ask.