Ah sis, very possible yan! A few of us din experienced ganyan, the breastfeeding really does mess with your cycle, especially if baby's still nursing a lot throughout the day. It's called lactational amenorrhea and it can kick in anytime, not just right after birth, so totally normal na biglang nag-stop ulit kahit may period ka na for a few months. Since negative ang test mo, I'd say just monitor lang and maybe check in with your OB next time to be sure everything's okay, pero honestly most of my mum friends sa situation mo it just came back once baby started eating solids more or nursing less. Hang in there!