I think it's more normal than you might think. I just want to cuddle with my therapist, and he is on my mind all the time... like an obsession.

If you think returning the letter will help then go for it, why not? Since I'm dealing with the same issue maybe I'm no help, but I am under the impression the best way to control the feelings is to accept them and tolerate them in the understanding that feelings come and go, and when we struggle and fight against them they persist and get more difficult to manage. Good luck to both of us I guess!