Speedometer going to zero then goes back up?!

I’ve been having this issue with my Camry to where
I could be driving and the speedometer goes down
to zero then the check engine light comes on. If I
stop somewhere and turn off and on the car, the
speedometer works. Sometimes when driving I feel
my car changing gears, I feel a slight pull. I brought
it to a mechanic who didn’t know what he was
doing (replacing steering fluid pump that didn’t
need it). i’m pretty much confused on what to do, i
don’t want to sink my money into this car as i’m a
high school student. it’s a daily driver, any
suggestions would be appreciated!