Ahhh I feel you, uncertainty macam ni memang stressful! Based on your cycle, since your period baru consistent starting June, it's still settling down especially while breastfeeding, hormones boleh jadi all over the place. The cramps without full period, then the light bleeding, negative UPT twice a few days apart, honestly, some mums I know went through similar cycles where their period just came in fits and starts for a couple months sebelum balik normal, especially if they're exclusively nursing. One friend said hers was so erratic she thought something was wrong, but turned out the breastfeeding hormones were just masking when bleeding would show up properly.
That said, since you're getting cramps consistently and a bit of fresh blood, and your cycle is still young, it could be your period is just... trickling in weird, or your hormones are still finding their rhythm, pero worth getting checked properly by your doctor when you can, just to rule out anything else and get peace of mind!