Wow! I could have written most of that. I know the hurt and confusion you must feel.
When my mother's birthday would roll around, I'd ask what kind of cake she'd like ...etc. She's always tell me she didn't want to do anything for her birthday. I'd give her many options for something fun to do, but, noooo. She'd have no part of it. The day of her birthday, I brought a bouquet of flowers from my garden. When she opened the door my sil, brother and their kids were all there having cake and ice cream. I was hurt but tried not to show it. Sil told me to join them but I said no thanks. Then I had to hear that I'm too sensitive and to get over it. This happened many times. I'd offer to help my parents with doctors appointments but was always told my car was too hard for them to get in and out of. (I had a large SUV). no matter what I offered, I was turned away but I wasn't supposed to act hurt. The final straw was when I offered to host Thanksgiving. I was told no and it would be at my brother house AND I wasn't invited. No explaination...... Things like this continued until my parents death when I wasn't involved in any funeral planning. I then told my brother I didn't ever want to see his face again.
Many other instances occurred during the years but I've already hijacked your thread.
I really understand. This kind of pain (and being told you're too sensitive) is very hard to take. I'm very sorry this is happening to you.