When did i conceive if u/s done on june 16, 2015 the crl was 0.76cm and ga 6 weeks 5 days...? also, is there anyway i could have conceived 4/11/15?

No: If the ultrasound dating estimate is 6 weeks and 5 days, then the conception date estimate is 2 weeks less, meaning 4 weeks 5 days ago. The estimate is an estimate, so conception could have happened anytime in the week before or the week after the estimated date of 4 weeks 5 days ago. That means in May. However, if the woman had NO sex since April 11, then the ultrasound dating might be wrong.