Why did I hear a thud and then only able to go 5mph

Last night driving I was at a stop light
and when I went to drive there was
kind of a jerk, so I go two blocks to
the next light and stop and when I try
to go to turn into a parking lot and
there was a thud like noise and my
car wouldn't go faster then 5mph
and all of my gear lights came on. So
I park and turn the car off restart it
and it won't go any faster and then
all of a sudden there's fluid leaking
underneath and the check engine
light came on! What is going on? It's
had all maintenance done regularly.
Any help would be so appreciated! I
don't even know where to start.