I'm assuming this is self stimulation? (I hate assuming)
If it helps you feel any better... I've talked about this with my own therapist, and have had several clients talk to me about the same thing. It can be talked about and lived through, believe it or not It's not wrong. I don't know anything about your past - but I can tell you that typically during self stimulation you have to feel very safe with your own body, and fantasizing about someone who is safe and secure is normal. T being that person, again, is normal. It wouldn't (or shouldn't) ruin anything at all.

If I have made the completely wrong assumption, please strike this post and remove it from record.