You should never feel bad for prioritising your health.
Jobs will come and go, can be changed etc. but your health will always come first.
If it's any help to you, I manage a small team of people and fully people, if you need tome off, take it.
I only ever need to know if a person is sick, and how long they expect to be out for (sometimes they may not even know).
I don't need to know the reason. Some people will tell me, some prefer not too. It's none of my business unless it's work related or they require support or changes on their return.
My view is I would much prefer someone to take the time they need, take it sooner rather than later (often waiting too long struggling means people are out longer) and not come back until they are fully ready.
No one know will they will struggle and it's rare for abyone not to have a period of sick leave for a 40 year working life. People don't become bad workers just because they need time off.
Don't worry about work. That's your boss's responsible. Your priority needs to be you.
Take the time. Recover. Only go back when you're up to it.