Should I retest??

My 3rd period is now 51 days late. Here are my details... My daughter is almost 8.5 months old (unplanned c section), I breast fed for 3weeks then switched to formula, for my first period pp at 5months, then my second 35 days later and now I’m 51 days with no sign of my period. I took a test at 40 days and it was negative. I don’t “feel” pregnant but my husband and I weren’t entirely careful (pullout) during the holidays... is there any point in retesting??