You're not cheating. This is a professional relationship, and your T made that very clear by not being as supportive as you need right now.

See the new T, see how it goes, and make a decision that you think is best for you.

I left my current T after a year. He was inconsistent in responding to emails, and there was way too many transference-issues going on. We were a very strange fit. I started seeing a female T, and was able to open up much better, without all the strong emotions based on who previous T reminded me of. Was considering riding it out, but after a year of anguish, I decided to do what was best for me.