Ok according to my first 6 week sonogram I will be 23 weeks on sunday but according to my recent 5th month sonagram I will be 24 weeks on sunday which one should be right.
I asked my Dr and she said if I went be my period I would be 26 weeks. which is the right sonogram?
I know the Dr. isnt right because my periods are not always the same length of days apart.
Also if I am 24 weeks on sunday does that make me 6 months pregnant?
I dont know how the weeks work.
Thank you for explaining.

I would go by the more recent sonogram myself.

As far as weeks -
Since it is rare that a woman knows exactly when she conceived, the doctor goes by a chart:
The beginning of the pregnancy is considered from the date of the last period. From there they count 40 weeks to arrive at an arbitrary date.

This actually allows 9 calendar months and 1 week for the pregnancy. It's just the way they do it to come up some sort of date. The baby is going to come when it wants to anyway!

Congrats and Godspeed!

If you know the first day of last period is the day they usually go by unless you continued to have periods the first few months of pregnancy.It doesn't matter how many days apart your periods are a women usually ovulates and then has a period 2 weeks later. So if you are irregular you ovulation day changes each month. To figure due dates they go by the first day of your period is day one so if that was on a Monday then the next Monday would be week 2. At this point you probably have not conceived yet, confusing isn't it. Then if you are a typically 30 day cycle you probably had sex and conceived. Then it takes about another 2 weeks before you can do a pregnancy test. That is why when you find out you are pregnant your are ususally 4 to 5 weeks before the test is accurate. Ultrasounds go by the growth of the fetus. Even with my self and our second pregnancy we new when we conceived the date on the ultrasound was off by a week compared to the date of the period. My OB went by the ultrasound date when we got further along. But in my case we had to do a planned C-section and we had to do it 3 weeks before I was due so I would not go into labor. At this point the ultrasound and my due date were with in the same week.
It is very confusing I would go by your period for now and say you are 26 weeks just to be prepared or next visit ask your doctor when you should expect the baby on his opinion which result should you go by. Just think you are over the half way point. Congratulations again. Some times science just can not be exact. Sorry I was not more helpful. Take Care!

Go by the most recent sonogram.
Just remember, you cannot accurately predict a due date every time. The baby will be born when it's ready to be born.