dccw, Your arousal fluid is clear. It is blood plasma that is squeezed from the cells in the vaginal wall when you get aroused and vasocongest (swell up).
Unfortunately you do not provide any context: Do you use condoms? Do you use a lubricant? Does this happen every time? Is it possible that you can have an STD or bacterial infection? Do you have any smells? How do you know it is not his ejaculate? Does this happen when you masturbate? Did this happen with other partners? Is the fluid wet? Slippery? Thick? Thin? Creamy?
Your cervical mucus can mix with all the other sex fluids. This should however only happen for about a week and a few days every cycle.
There are some thought that fluid from the Skene's glands can actually come out through the vaginal walls, and not the urethra. The Skene's glands are the source for female ejaculation. This fluid is white and sweet but should nit be a 'quite a lot'. A teaspoon or two at most.
There are also 4 gland openings that produce differing amounts of fluids in the vulva floor. The Skene's glands next to your pee hole and the Bartholin's glands next to the vaginal opening. The purpose of these fluids are not known. It is thought to be anti-bacterial and lubrication. Especially the Bartholin's glands fluid will end up in your vagina.
It sounds like normal cervical mucus mixed with your arousal fluids. The odds are also better that you will masturbate or have sex when you have cervical mucus because your ovulation hormones makes you horny. So you should notice that more often than not.
If there are no itching or smell, it is unlikely to be an infection and since you get it with the dildo as well, it is unlikely to be an allergy.
Fluids from your vagina normally does not have anything to do with sex unless you are sick.
Every woman have different fluids coming from your cervix and vagina at different times in your menstrual cycle. Creamy when you are between fertile and infertile days, wet, stretchy and clear when you are fertile and maybe just before your period, period debris when you are menstruating and clear slippery fluid when you are sexually aroused.
Stomach pain can be a sign of ovulation or menstruation. Both these times can have cervical mucus come from your vagina.
If it is chunky or smells bad or it burns or itches a lot, you should see a doctor.
Remember to only wash with clean water. Do not douche and keep strong or scented soup away from your vagina and vulva. Also wash under your clitoris hood. Don't use scented sprays or pads. Your vagina cleans itself and it is very sensitive to things that can disturb its balance. Anything sweet/scented is very bad for your vaginal health.