Got pregnant on birth control

I was taking birth control pills regularly and got pregnant. My last period was only 2 days and very spotty (never the case with me). OB says I'm 23 weeks based on that menstrual date but I feel farther along. And then I went into the hospital for round ligament pain and my measurements showed I was 25 weeks. Have no clue how far along I actually am... Experiences/Thoughts welcomed