It has been about a month and a half since my miscarriage.....

I would recommend going to the therapist - even if you think you don't need it, I think Samuel might need for you to go, for whatever reason.  And if the therapist also agrees that you're doing fine, perhaps that will get him off your back on this issue for a while.

Worst case, it's an hour of your life you won't get back.  Best case, you'll have an opportunity to talk to a third party and it's an hour that someone else is watching Caitlyn!  :)

As for when you'll be able to get pregnant again, that's more a question for your OBGYN.  Because of the complications with your miscarriage, it wouldn't surprise me if he/she thinks you should wait a little longer before trying.