So whenever I have been driving recently if I go a little too fast my transmission will start to shift harder in the second and third shift, then the O/D light starts blinking. Do I have a transmission problem?

 

Well, it is definitely telling you something is wrong. See if you can get a decent scan tool that can do transmission codes and find out what pops up.

I think your local parts shop may have this service for a few bux or even free. My local is free, but I went and bought a BlueDriver OBDII reader for 100 bux off Amazon. Me likie that I don't have to drive anywhere to see what may be brewing in my truck anymore.