Manipulation isn't a joke (TW vent)

I've been manipulated multiple times in the past even now when I'm in a vulnerable state of mind I can be manipulated. I have a story about my ex where I thought I could trust him and he ended up manipulating me into sending him things that made me uncomfortable I can't take what I did back and I hate myself for even agreeing with it in the first place. that situation has made me uncomfortable with my body but even due to it I just can't say no to people. Which makes it harder for me because that also allows people to do what they want when they figure out I barely say no. being stuck in a constantly vulnerable mindset and barely saying no could affect me in the future but I don't want to talk to the therapist I have now because she will be stuck on the part of the manipulation. I know what my problem is but I just don't know how to fix it.