Thank you for reaching out to us.
We are sorry to hear of the abuse that you suffered and of the difficulties that you have experienced as a result.
Even with no history of sexual trauma, many women find it difficult to bring stains for halachic evaluation. For women who have survived abuse, this can be even harder, and other aspects of niddah observance can be especially challenging as well.
We deeply respect your commitment to observing these laws notwithstanding the challenges, and we appreciate the opportunity to offer you support while respecting your boundaries.  Sometimes, reaching out to a counselling professional can also be helpful in fine-tuning where those boundaries lie.
We do have some thoughts and ideas for you.
First, this may be a color that you can evaluate on your own. A light brown (e.g., the color of coffee with milk) with no reddish hue is not a niddah color, and can be disregarded. If your stain was that color, then it did not disrupt your clean days. This is true of bedikot as well. They do not have to be completely clean. See our article here for more details about evaluating colors.
If the stain is a darker brown, or if you’re unsure whether it has a reddish hue, then it should be evaluated. If it would be helpful to you for a woman to evaluate it, then please see our directories of Yoatzot Halacha in Israel and worldwide. Often, stains can be evaluated anonymously, by using drop off boxes and a dedicated email. You also might find the process to be somewhat easier if you cut out just the stain rather than sending the whole garment.
Alternatively, the Tahor app could be a good option for you. It uses special color-calibration technology to allow women to photograph stains or bedikot with a smartphone and send them for remote rabbinic evaluation.
If the stain requires evaluation and none of these suggestions will work for you, it is permissible for you to decide to do a new hefsek taharah and restart your clean days. This would delay your immersion, though.
We wish you continued healing and strength. Please reach out to us with any further questions about any aspect of these halachot.
May you see many years of nachat from your new baby.