We actually have a lot more agreement and information than we used to on this. That said, in general, ejaculation from folks with a vulva tends to be clear and thin, and does tend to come from the urethra, not the vagina. It also will tend to be something where you know and feel when it happens, rather than only finding evidence of it post-orgasm.
Unfortunately, what no one here or elsewhere *can* do is tell you for sure what your particular fluid was you're asking about, both not being present, and without being able to analyze that fluid in a lab.
From what you're describing, this sounds more likely to me like it was a mix of regular vaginal/cervical discharges from your fertility cycle, as well as fluids that can happen when we're aroused. Because orgasm usually involves muscle contractions of both the muscles of and around the vagina, and the uterus, post-orgasm fluids like this appearing like yours -- and not seeing it before orgasm -- did can be pretty commonplace. I'm not sure what you mean by the straight line pattern you are talking about, but I don't see why how discharges (which is what we call anything coming out of the vagina, ultimately, as it is being "discharged") appear would mean they aren't discharge. Maybe I'm not understanding something you're saying?
I would keep my eye on things because thicker or additional discharges can sometimes be part of an infection, like a yeast or bacterial infection, or some STIs.
I would also say that ultimately, if it isn't a healthcare issue, it doesn't really matter what comes from the vagina or other parts of the genitals with or during any kind of sex, including masturbation. An array of fluids tend to be a common part of sexual activity, and all those fluids are just fine, you know?
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