Generally there is a cause & effect for your pain symptoms. Spoken differently, if pain is attributed to a tooth, generally an x-ray or visual exam by the Dentist will reveal an abscess or cavity, etc.
However, it is not extremely unusual, for pain to be come on and the abscess or cavity doesn't yet show up on the x-ray or visually either - or at least not yet! What I would recommend is either going back to the Dentist whom you first went to, or, alternatively go to a different Dentist (your choice), for a second opinion. Time has elapsed since your last visit to the Dentist and hence something may now be more evident either visually or via an x-ray. Plus a second set of eyes can't be a bad idea as well. As for why both the top and bottom teeth hurt? You ironically could have two separate problems... true, but also there is often something called "referred pain". Referred pain can cause adjacent teeth to be hurting, or an upper when it is a lower, or vice-a-versa.
Summarizing; If it's been more than a couple day since your first Dentist looking and not finding the problem, I'd suggest seeing a second Dentist or revisiting the first (your call). Often times, what doesn not show up on Monday, will show up on Wednesday - acute pain can be that way, and I suspect your acute pain may now be more evident and treatable because it hopefully now can be better diagnosed, as it's had more time to develop & demonstrate itself either visually or via another x-ray. I hope this helps you!
*PS: If I can assist any further, please do not hesitate - OK? beat regards ***** ***** Dr. Rampton