Important question

I'm getting married next week I'm pregnant 5 months now BUT I have a problems so here's my long story short so the first time I went for an ultra sound to find out how far along I am I got a due date of July 7 bc I was not aware of when I had my last period bc my periods are so irregular so the ultra sound was very necessary. Then at my 18th week I finally had a OB and I went for a clinic closer by my house and more convinient for me. Anyways long story short I got the 2nd ultra sound at 20 weeks and they gave me a died ate of June 26. I told her it's a different due date then the first untra sound I got which one should I go with y'all? I'm so confused of when I'm due