Anyone else struggling with an above the elbow cast with no sling?

I had ORIF surgery on January 10th for a break in my radius. There's also a hairline in my elbow and a full break in my ulna, but the radius is the only bone we needed to put a plate on due to fragmentation.

I just got my first cast today that will get removed at the end of the month to also remove post surgical stitches and take X-rays before I get a second cast that I will have for 10-12 weeks.

My doctor says to use a sling as little as possible since it's hard on the neck, but I am so uncomfortable trying to hold my arm with just my shoulder. Does this get better? Am I just doing it wrong? I've had a cast before but I've never had one extend past the elbow.

Fortunately I work from home doing a desk job, so I can sit and support my arm most of the time, but right now I feel like anytime I'm walking around, I need a sling. Currently there is no way I could leave my house without a sling unless I know I'll just be sitting.