"Would need to be something I could use during the day while at work. "
Cannabis suppositories work well! You can use them for back pain AND menstrual cramps. Just be sure to wear a panty liner that day!:)
The main three things I recommend for menstrual cramps are tinctures, suppositories, and topicals. All can be used discretely if you choose the right product.
Moxie Meds has a 4:1 CBD:THC tincture that has a very mild scent and is potent, so you don’t need to consume a lot. It can be dropped in your mouth or added to a beverage. The high CBD ratio means you can experience pain relief while keeping psychoactive effects to a minimum. I use 2-4 drops under my tongue for cramps.
Foria offers suppositories for menstrual pain. These would be undetectable and provide relief from cramps and associated pain.
Topicals are fantastic for lower back pain. Sweet Releaf offers a topical that has a very mild odor, it smells more like a moisturizing balm. At home after work I suggest Om Edibles topical oil paired with a hot water bottle or heating pad. The scent is slightly stronger with that oil, but it is very effective. This is the most effective treatment for lower back pain from cramps.