Many people want to say no to things. It's something they truly would like to do, but they feel awkward, they don't know the right words or how to do it graciously or politely. They need a few skill-building sessions and some practice so they'll know what words to use and how to use them politely.

Your situation is more complex. It's deeper. Probably goes back to some bad things that happened to you when you were young or that you saw happen around you. It's all right to have a deeper, more complex situation than just having to find some polite words. That's your situation and it would probably be good to spill everything to T so she can help you in a more realistic way.

This sound like a deep-seated fear. People can get over such fears, but it takes some extra work and different techniques. If you level with your T, she'll probably be able to think of some way to approach it, but the two of you may have to talk about it for several sessions before the fog clears away.

In a way, being afraid to say no isn't any different than having a fear of flying or driving a car or walking under a ladder. And all of those things can be treated, so this could be a very hopeful situation for you, as long as you get honest with your T.

I wish you the best.