Bleeding between periods- normal?

I'm waiting for test results from my doctor, but in the meantime, I want to see if anyone else has had this.

For the past 15 years my periods have been very regular, and I've never had spotting between periods. This past year I've started spotting mid-cycle, and this past month it was so heavy I had to use tampons for two days. When I logged spotting in my log in this app, I got a message that says mid cycle spotting is normal around ovulation. However my doctor was concerned when I told her I've started bleeding between cycles. Has anyone else had changes in their cycles as they got older? Or sudden mid cycle bleeding that you never used to have? Thanks ladies.