Busted Transmission??? Maybe

Hello Everyone im new to this forum and not very Car literate but I think this problem im having is transmission related.
Ok basically I was driving home and I heard a loud *thud* and then my car starts loosing horsepower but im still applying same amoutn of pressure to gas pedal. So I popped it into low drive and it kinda caught back up but its like it is not registering the gear. It will reverse no problem but as soon as it is put into Drive it sits just like it had been placed in neutral.
Anyone have any ideas????

Yeah kind of sounds like the tranny took a dump.Check the fluid level with it in park and warmed up also check the color of fluid and smell to see if it smells burnt and is dark in color.

Do you think that a simple fluid change and filter change would fix it???

no don'r change the fluid u will waste your money. you need a new trans, the fluid will actually make it worse. your trans is used to the fluid in it so a new fluid with be bad. at least that's what they taught me at UTI, the best mechanic school in the country.