I don't know you, but am only assuming you're a new grandma??!! What a beautiful baby...and I'm sure that you were greatly appreciated and needed by the new mom!
Now- back to you. Sounds like you're so used to taking care of others, that you haven't taken time to take care of you! The hardest thing to do is make yourself a priority, especially if you don't feel worthy. I say that you've made the first step -- recognizing that feeling, and seeking help!
Take some time, get alone, and think about YOU. I'd suggest writing things down. What do you want for yourself? What makes you happy? What do you want to change? What do you like about yourself? Just take an inventory of your life, and find the positive things to focus on....then pick ONE small thing you want to change, but make sure it's something that YOU have control of. You can't control how others feel about you, what they say to you, etc. - but you CAN control how you react! Eleanor Roosevelt once said something like "no one can make me feel bad about myself without my approval" - and I think it's a great thing to remember!
Just know that you are important to YOU!! YOu need yourself -- to take care of, to love, to talk to (yes!) -- so start by recognizing how special you are to yourself!
Best of luck!