Transmission

Hi, sounds like it's in limp mode. This can happen even when you just change the transmission oil, let alone for other problems.

Firstly, I would disconnect the battery overnight if you can. Reconnect it and drive. If you're lucky, the TCM will reset and clear the memory of errors it's picked up.

If problem persists, and you are not having any warning lights come on, then it may be something such as the input speed sensor, or the shift solenoid pack. These can get gummed up and sometimes varnished if old oil. put in something like seafoam transtune and let it remain in your tranny for a week or so. If the car is still stuck in 3rd, run the engine and keep shifting through the gears for about 15 minutes, this will work the solenoid.
If it is the solenoid, what you will notice is when the engine is reset, and you put it in srive, there's no jolt or jump. When the car is in limp mode, it will give you a slight jump into gear like it is seeking to lurch forward.

If you are lucky, then this may ease off over a week. The other thing is, when did you last change the transmission oil?

Before you start changing parts on the car, after disconnecting and reconnecting the battery, take the car to a parts supplier like o'reillys and ask to use their engine fault diagnostic tool. This will give you the codes of faults which you can look up.

If you end up finding some faults with the ECM, TCM, etc, shop around for module suppliers as the factory ones are very expensive.

Lastly, if its mechanical, then you'll have no option but to take it into a trusted transmission repair shop who'll be able to run a road test.

good luck.

1999 honda accord dx 4cyclinder when slowing down and getting back to the gas sometimes the trans dont fill like it dounshifts fast enough and check engine light comes on