Hi. Just wanted to offer my experience.
Had a D&C in November 2014, after a MMC. After that, my period came spot on 28 days the first month, but like you I had brown stringy spotting however this was mid cycle.
After this, my periods were not as regular as they had been. (I'd always had 28 day cycles). They were now anywhere from 28 days - 34 days, which was really hard as every time I thought my period was "late" and I might be pregnant, I would be greeted just a few days later with the witch. My periods did change after my D&C, and nobody believed me until I found my current GP.
For some reason, after my D&C my periods were quite light, then heavy, then light, then spotting. Not normal.
It then took me 18 months to successfully fall pregnant, which my current GP put down entirely because of my D&C. My cycles were so irregular and my lining wasn't shedding properly, and was too thick for a successful implantation which resulted in numerous chemical pregnancies over those 18 months. My GP first time I saw her, told me to try low dose aspirin as it would help thin the blood and create more blood flow in my uterus, and surprise surprise, we fell pregnant that month and are due in just over a month!
Definitely seek more opinions and don't stop until you're happy with the results.