Wow that is a crazy long wait. I have waited 8 weeks before, but not 5 months.
Can you ask to be put on their cancellation list? Maybe that will move you up sooner.
Otherwise, I'd suggest shopping around. Gps are usually happy to change the name on the referral letter. Give a few different places a call and book an appt at the one you can get in soonest. Then have your gp change the referral.
During the wait period there are some great mental health places you can call if you are finding it difficult to get by. The Beyond Blue line is available 24/7.
Kind thoughts Jess