Early miscarriage/failed pregnancy?

We’ve been ttc for a while now - 8 months actively trying and a few more casually before that. My 26 day cycle is usually as regular as clockwork, always lasting 4-5 days with a medium flow, and always with clear pms signs the night before.

On two separate occasions, 4 cycles apart, I’ve had heavier bleeding, which came on suddenly without any warning and lasted up to a week, starting about day 21 which I think is around the time that implantation would be starting if the egg happened to be fertilised. Cramps only began several hours after the blood appeared which is never the case usually.

These two occasions were definitely unique to what my cycle usually is like and both times the next period was perfectly normal, coming exactly 26 days later. I have been noting my cycle, periods, ovulation etc very carefully with a calendar since we’ve been trying so I know that I haven’t made a mistake. I didn’t take any tests as it was much earlier than I’d expect to have a result and I can’t find much info about this online. I’m not sure if it’s worth seeing a doctor as it would have been too early for them to check hormones at that stage, but I’m thinking that it’s two times now and if it keeps happening it can’t be a good thing. Health-wise everything else seems fine and nothing else about those two times was different, no added stress or illness. Any experience on this or advice would be appreciated.