What kind of enclosure do you have.Take a picture of it and post it here, it's very possible that the top of enclosure is screen, you might be losing humidity just as fast as you're putting it in.

I may have gone way overboard on my enclosure but it works very well.
I have a EXO Terra with 3 inches of Coco fiber that is moist enough to clump.
I do not use a water bowl because he never used it.
The main source of heat is a 50 W ceramic heat element.
And a zoo med fogger both are also controlled by a HT 10 hygrotherm.
I have a secondary source of heat which is A zoo med micro heating pad attached to a large ceramic tile that is placed under the terrarium
And not attached to the bottom glass this acts as a indirect source of heat from the bottom of the terrarium.
I've had to do this since my wife likes to keep the temperature in the house 63° and that is much too cool for my Pac-Man.
Sensor placement is critical I put mine in the back of the terrarium halfway from the top. The furthest corner from the heat source.
This will create a thermal gradient inside the enclosure where there is a hotspot ranging to cool that way the frog can choose the temperature he likes.
To add to the stability I placed small sheets of plexiglass that is one eighth inch thick on the top of the screen to keep in the moisture.
Just make sure you do not place the heat lamp on top of one of the sheets it will not do well
I have also covered the sides of the enclosure with aquarium background material this lessens the stress on the frog.
And here's the gone over part.
I bought a $40 IP camera that can pan tilt and zoom and used hot melt glue to mount it upside down on the front part of the screen
Now I can keep an eye my frog when I'm not home and traveling.
I'm trying to work out a way to be able to interface the HT 10 and be able to check it remotely.
Also if any of the parameters go out of range have it notify me.
Hope this helps.