I've been in your position. If you're not comfortable giving the whole truth you don't have to. My schoolwork suffered because the week before the start of the semester, I was in the hospital. Returning back to real life was a difficult transition. All I had to tell my professor was I was in the hospital, I can get a note if you need it. He was very cool with it. Later, same class, I was suffering a lot and couldn't get any work done. I just got a note from my therapist - usually they don't care about the dates or whether the note is an excuse for absence or your wellbeing overall. In fact, I just explained it as health issues.

If your grades are suffering and you believe you can get help, it might be a good idea to voice these concerns.