Hi Becky - Here is a "stepped" test you can try to see if you will be safe (I traveled for 35 years in my job and had eustachian tube disfunction, my ENT taught it to me)
1) Get a decongestant nasal spray and use it ONCE - if the tube unblocks, even temporarily, you are safe to fly.
2) If that doesn't work, take one dose of pseudoephedrine decongestant - again, if it works, OK.
3) Try the 2 decongestants together - again, if it works OK.
If none of these work, you may have a very painful trip. Twice I ruptured eardrums by ignoring this...
Then, if one of your trial works, do the same thing 30 minutes before the flight, and use a shot of the nasal spray 15-20 minutes before descent. Also, chewing gum or sipping water during the flight helps keep the tube open.

Good luck - it is awful to have to cancel a long-awaited trip!
Sue