Is it normal to masturbate while thinking about my counselor/therapist?

Change therapist.
While it is normal to feel attraction for someone, it is not normal or useful if that person is your therapist.
I suppose you are going there to seek for help, but you won’t meet your goal if you feel that kind of attraction for her

Tell her you have an itch in your vagina and ask if she’ll shove her fingers up there and scratch it for you.

What you're experiencing isn't unusual. Many women have at least occasional sexual fantasies about other women, and it's fairly common for people to become sexually fixated on their therapists. If you're being honest and open with your counsellor, that can lead to you feeling very emotionally close to her in the intimate setting of your sessions, all sorts of repressed emotions can break free and that can lead in turn to you becoming sexually interested in her (or at least in her professional persona).

Obviously, if these feelings are so strong that they distract you from the work you're supposed to be doing with your counsellor, that's not helpful to you, but they can also highlight hidden issues you need to sort out.

The term for it in the psychiatric community is "erotic transference", and any well-trained therapist or counsellor should be aware it. I suggest that you discuss this with your counsellor. If you're too embarrassed to be specific (and I suspect you would be), use the jargon, and say some random internet guy suggested that was what you're experiencing.

https://www.psychologytoday.com/gb/blog/in-therapy/201206/clients-guide-transference

As long as it isn't affecting your treatment then it's harmless.

Idk if its normal you should ask your therapist

Is she helping you with nofap?

It's very unhealthy. Tell her, so she refer you out to someone else.