measuring almost 3 weeks behind

so i am looking to find out if this has happened to others and if you ended up with the blessing of a baby or if you suffered a miscarriage
i went for my first ultrasound today and based on LMP i should be 8 weeks, i measured in at 5 weeks 4 days with what looked to be the start of a fetal pole, the only other time i measured behind was when i miscarried but there was a baby that didn't have a heart beat at that time, now i also just stopped breastfeeding my daughter in July so i know it is possible that my cycle may have still been off from that, I am looking to see what has happened to others, i plan on calling my dr in the morning and talking to them about my blood work that i had done a few weeks ago, if i find out anything i will let everyone know that posts here what my outcome ended up being
Thanks for your responses