baby size vs pregnancy in weeks

Shannon

Ok, so I am a tad confused. I went to the Dr two weeks ago for my sonogram. according to this app I would have been 7 weeks. My sonogram was scheduled for checking on a cyst, NOT a pregnancy, but since I was pregnant we checked on the baby. it was very small and they assumed I was closer to five weeks but according to my period I was around 6 weeks and two days (I had two periods so it came out different than Nuture). despite this the baby measured at around 5 weeks with a 93 heart rate. the doctor said he wasn't worried since the baby is so small but I go again this Wednesday to check. I SHOULD be at 8 weeks but my symptoms are all gone besides mild cramp/stretching feelings in my uterus. I am probably just paranoid because we just had a miscarriage and this pregnancy was very unplanned. I am very bloated and I am a very lean person...idk...this post is all over the place but has anyone had something similar? a baby that is growing slightly slower than your pregnancy week?