High risk not sure of due date

Jeni

I have irregular periods so my doctor can’t tell me how far along I am and won’t give me an ultrasound until end of April! I ovulated and had sex on the 18th of February, I did a beta hcg that was less than 2 on the 24th of February and another on March 6 with a level of 98. How far along would you guess I am? OB says I’d be 6.5 weeks on April 26th… that doesn’t seem right.