First Job Issues

I recently got my first job requiring a CDL. I got my class A a few months back, but covid upset everything.

It was listed as local work, which it is in the sense that I am home every day - if I work a 12 or 13 hour day. While I did get my license on a manual, my first job was to drive a straight truck (not a tractor trailer) 5 hours into the mountains with a 30k lb load of marble, which is a max load for the vehicle. I had never done anything like this, and it was a harrowing experience - there was an accident and construction in the mountains where I had to figure out how to handle the vehicle in low gear with that load at a crawl uphill, and kind of learn on the fly how to downshift coming down a mountain - though it was technically covered in the course I took to get the CDL.

On Monday I am scheduled to go through the Appalachians again from Baltimore to Pittsburgh and back, and I am frankly worried. I was exhausted and grinding the gears by the time I got back to home base last time. The first trip was very difficult - is it me and my lack of experience or would this be difficult for anyone? Is it reasonable for my employer to expect me to be doing this? Its a small business, and I am the only person with a CDL to drive this truck. I think the owner believes that if I have the license, I should be able to handle this no problem.

Any advice on how to handle the situation (while hopefully keeping the job) would be welcome.

 

Thanks guys. I appreciate the support - it sounds like the consensus is that I can do it and I shouldn't worry, just be careful. FYI - this is the only picture I have of the truck, unfortunately its from the back, but its a triple axle manual 10 speed:

 

I live in Silver Spring, hauling out of north Laurel. Guess I'm headed to Pittsburgh tomorrow! I've just been worried because with the first 7 gears used at 25 mph and below, when I have it loaded, I don't know which gear to put it in necessarily - especially if I'm on a grade in the mountains - so I frequently wind up grinding a couple gears looking for the right one. I don't want to damage the truck, and its stressful when there is traffic/accident/construction. My forearms are sore from gripping the wheel so hard last trip.