Hard to say.
Could/can you insert your finger into your own vagina and use tampons pretty esily? If so, you disn't have a full hymen to begin with. Sexual intercourse is NOT needed to erode a hymen: in most cases, it does so on it's own due to regaular physical activity, masturbation, tampon use and menstrual flow.
And you're right: if you've had intercourse before, you most certainly had only a partial hymen, or your hymen may have been fully eroded before then, as well.
If sex is painful and you're bleeding this many times in, it's likely what was going on was that you weren't aroused or lubricated enough (be it naturally or by using enough latex-safe lubricant). Too, during certain times of our monthly cycles, we're a bit drier overall than others, and during those times, even when we're highly aroused and wanting intercourse, we may find we need to use a bit more lube than usual.
But rule of thumb: sex ever hurts, stop, figure out what the problem is, and adjust it. You don't want to be hurting yourself, and why would you have sex if it didn't feel good?
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