Some Americans will use the simple past in the context, so we may have new members who would assert the simple past as just as good here, though I hope not.
No, the "until this morning" is implicit. If you'd been sick for two weeks, you might say, "I didn't have any problems for a long time. Then two weeks ago, I started getting ..." This would be a correct usage of the simple past.
Similarly the doctor doesn't say, "It was a long time since your last visit" even though that time has already finished, since the current visit is in progress.
You're allowed to include changes in the immediately recent past and still use the present perfect. "I've just finished ...", "I've just arrived ..."