Be careful of your boss. He may be playing nice guy to you, but reporting to the office manager all kinds of things.
I totally agree with this statement...though it depends on your situation. How long have you been employed there? Is it a big company with an HR department? How is your relationship with your boss?
I have been dealing with this myself, in some ways. I have had a generally good working relationship with my boss (same job/boss over 9 years) and I went to her immediately when I started feeling like something was wrong because I wanted to get it out there that some health issue may be (in my own opinion) affecting my performance. She was (and continues to be) very supportive, though there were times when I felt very stressed/anxious about
asking for any time off or time to go to appointments, etc...even though she repeatedly said "do what you have to do...health comes first". I was constantly thinking she was just saying the right things to me but keeping tabs.
I became so anxious about
it, that I had to express my concern that this is impacting my position/future, and asked if I should contact HR just to get a formal sense of my options. She again expressed her support, brought me back to reality, and no need for HR. This was then validated with a good annual performance review and other positive year-end outcomes.
So my advice is just be honest as you can if your relationship allows it and try to work out an informal "flexibility agreement" of some sort...even if you can do it in stages, say for the next month or so until you have more regular improvement. If your relationship is good, maybe you can ask your boss to talk to the office manager to explain your situation.