I read though many post but have not found anything like the problem I am having and if so I am sorry. Like to figure out something before I take it in

I have an 04 F150 with over 100,000 miles on. Started yesterday and today worse. The fluid is fine. Only issue I am having is around 30 mpg when the transmission (auto) changes gears. The motor rpms will rise but the trans does not shift correctly. Now starting off or on the highway it will down shift everything works but around 30 mph. A few times it will shift without me noticing anything other times it will take a bit to shift still in gear but shifts at higher rpms and rest of the times rmps will jump up and the truck is in neutral if I get go of the gas it will shift. No clunk or shudder

Thanks for any help...