General Conversations

I moved from a GS7 position into a GS7 max position that is labeled as Assistant/Clerk. I took this position as I felt it was a low stress job until I completed my degree. I interviewed and was told the job would mostly be handling travel for 30 people and other assistant duties as needed. After the interview, the supervisor said my personality made her believe I would be perfect for other major duties as well. I was bombarded with major responsibilities and the staff was not very eager to help me learn them. Shortly after we were made to telework due to COVID. I have been doing my best to figure most things out on my own by looking back over saved documents and things. This has not been a healthy job. The workload is major, everything is recurring weekly and there are timelines on all of it. I asked about a promotion since the duties I am handling are not assistant or clerk duties. They are very clearly specialist duties. I was told sure but it's my responsibility to make cert. It's been 7 months since that conversation and I have not been able to make cert in the specific 301 series to a specialist.
I feel so stuck between a rock and a hard place. I am trying to balance virtual school for my kindergartener, college and this demanding and heavy loaded job. MY boss very much knows this yet keeps piling more responsibilities on me. I recently had to take leave and be placed on meds for the stress and anxiety.
Any advice on being in a clerk/assistant position and having to carry out specialist workloads and tasks? IS this kind of thing allowed? HR won't discuss because I asked to keep it confidential. Forgive my complaining... I am just looking for some advice as I am fairly new to the government. Thanks!