If he is not available, you should try to contact him via email or phone and ask how to handle his (lack of) availability.
Simply put, if he isn’t available regularly for you to confess ask him outright if it would be acceptable to confess with another priest or if it is a requirement to confess to him (if so, ask for clarification if it for every confession or at set points).
We need to confess our sins. If you have mortally sinned, and you can confess in 2 hours, it would be weird to wait for three weeks. Not to be dramatic, but what if you pass away? You did have the opportunity to confess.
Also, you need to talk to him about his availability in general if you feel like your discernment isn’t being prioritised. Priests are people, and if he has too much on his plate and is not able to meet your needs then he may be able to refer you to someone who does have the time for you.