92 Honda Accord popping out of 5th gear into Neutral

Hello,

My Accord has been doing so well, but recently it has been popping out of 5th when I push the accelerator, but if I'm over 50mph (2 rpm) then it will stay in gear. Any insights?

I just checked and I am most definitely due for an oil change, but could there be anything else I should have checked??

Thanks!