Ako rin, mama, parang ganyan ang nangyari sa akin with my second, walang period for almost 8 months kahit nag-breastfeed lang ako at nag-pills na rin, so hindi ka nag-iisa dito! Kasi ang mixed feeding and the pills together, sometimes they really mess with your cycle, plus every baby is different talaga. Since negative ang PT mo, I'd still suggest checking with your OB lang para ma-rule out and ma-confirm kung it's just the hormones settling, plus peace of mind, kasi lingering worry lang if hindi mo ma-address, no? One of my mum friends waited it out thinking the same, pero after consultation she found out may minor issue lang that was easy to fix, so better safe.