advice on dates?

Hey everyone this is my first pregnancy. I went to the doctor on february 14th thinking I was at least 8 weeks (8 weeks and 4 days really) but they said I was only 5 weeks and 6 days!! Has this happened to anyone else? Because I am a little freaked out. I took a pregnancy test on January 13th and it was positive (this was before my missed period date). I will say my periods are longer than normal 32 days usually and I was under a lot of stress during the new year because one of my dogs ran away and we were traveling. Please let me know!