Christina
You are probably seeing sphinx moths. Here in Pa. it is unusually warm and DRY :(( I am still seeing them at my datra (angel trumpets)

Here is a link that might be useful: Hummingbird moths

Hummingbirds do like morning glories and they do fly forward bacward as well as straight up and down like an winged elevator but they generally don't feed after the sun goes down. I agree with Earline,you may be seeing sphinx moths also known as hummingbird moth. Most fly at might and are rarely seen. A few species, however, fly during cloudy afternoons and at dusk when they feed at flowers in a manner similar to that of a hummingbird.

Penny