What is this pop/thump sound during acceleration?

What is your question?

I noticed a pop/thump a few months ago out of the clear blue. It made the car hesitate to go for that split second it made the noise. I could feel it under my feet as well. It continued to do this once a day but only like every few days or once a week or so. Last week, out of no where it started to do the thump/pop like crazy and is still doing it. Check engine light came on. Took it to Auto Zone, they said a misfire in #2 and #3. Coolant reservoir keeps coming up empty, had oil down insode spark plug #1, oil level keeps showing empty on dipstick too quick. Replaced head gasket assuming it was blown in between #2 and #3. Still having the same thumping/pop during acceleration. Fine in park, starts great. Engine mounts r bad but this sounds more like a backfire/misfire but in the front of the car. Any help is appreciated. Very lost.