Even though I'm a male, I had this experience with my ex. My suggestion is just as reliable as yours. Your opinion may not be the solution either.
Hi becca242. Spotting or bleeding during sex is most likely caused by the penis bumping the cervix, thus causing breakthrough bleeding from the uterus. This usually happens when the cervix is positioned lower in the vagina and easier to be bumped. Depending on the timing of ovulation, the cervix will be situated higher or lower. The latter being the most frequent position the cervix can be found. This may account for the randomness of the bleeding you experience. I don't think it has much to do with the vagina being open for penetration, so skip the suggested dildo.
sounds like your vagina is not fully open enough for penetration. try penetrating yourself with a lubricated dildo (fake penis) in your spare time to help your vagina become more and more use to real sex.