It sounds both like you have a busy T and your own wants for scheduling are getting in the way? With the upcoming 5 week one made, did you ask to make another for only 2-3 weeks after that, right then, while his schedule is clear and you'd be "first"? That way you could, at the 5-week session, leapfrog 2-3 weeks and reverse being at the "end" of choices each time?

If he only makes one session at a time and he's busy and you are too, you might have to switch to a different T or decide therapy is more important than missing a little more work so you have more choices?

I have my groceries delivered and I can go online any given "Tuesday" and get delivery on Wednesday morning, first thing, but I can't go online on Friday and get delivery for Saturday morning because everyone who works is off then and wants deliver then. I suspect everyone would like an after work appointment but there aren't very many of those but if you picked a day where you left a couple hours early (and made up those hours by offering to come in early, work late, or work during your lunch hours the other days) you'd probably have appointments as often as you wanted?