I think you should go back to your GP about this. She should be able to tell you how long it will take for your blood sugar to return to normal after you stop the pills. You probably need to see her anyway to get something for the thrush.
Abnormal bleeding at age 45 could be due to a number of things. Ask your GP what things she has ruled out and what things she still has to rule out.
First thing was pregnancy. Next was probably cervical cancer. A smear test is usually the first way they try to check for pre-cancerous changes or cancer itself. But a smear test sample can't be viewed very well in the presence of even a small amount of blood. There are probably other ways to check for this, I don't know.
A blood test for certain things might be helpful. I assume she has considered this or done this.
An internal examination can show if there are noticeable-sized cysts, fibroids, or structural abnormalities like that. However, if these are small then an ultrasound is needed.
There are two methods for pelvic ultrasound - either the sensor is pressed onto the lower abdomen, or a probe is inserted into the vagina. These different angles give different points of view. I can't see why even the latter option would be a problem if there was bleeding, but I could be wrong. Ultrasound scans can shows cysts, fibroids, growths, tumours, and also how thick the lining and (I think) the wall of the uterus is.
If she meant a scan where the doctor inserts a speculum and looks at the cervix, or inside the uterus, then that might require bleeding to stop first.
If all of these methods fail to show the cause of the bleeding, another option is exploratory laparoscopic surgery. I have no idea whether this would be necessary or appropriate for you at this time or in the future. This surgery is the only way to check for endometriosis.
When my mother was in her late 40s, her periods got heavier and then were super heavy. At 51 she had a hysterectomy and they found the wall of the uterus was thickened. This was thought to be due to endometriosis, which I was diagnosed with in my 20s.
Endometriosis can cause increasingly heavy periods, but I would think it's noticeable earlier in life than the 30s.
Heavy periods that don't have a clear cause can be treated with medication. I think your doctor wants to rule out other things before trying ongoing medication.
Uterine fibroids are very common and can cause heavy bleeding. It's possible you have them but your doctor couldn't feel them. Please note I only said possible. If you have them, it's not like cancer, they are benign and can be surgically removed.
I don't know much else about heavy bleeding or its investigation, and I suggest you ask your doctor where things are at with getting this diagnosed, and that you also tell her about your concerns about the raised blood glucose levels and the thrush, as these will be making you feel horrible, I imagine.
She should also check your iron levels in case you are getting anaemic from the heavy bleeding. If you get iron supplements make sure you don't get constipated from them.
Good luck.