N.M.
My 20 mo old is finally talking a little more, but there have been days when it seemed like all he did was fuss.
My question, as well, is how does she make her normal needs known? Is she talking yet? Pointing to things or bringing objects to you for your help? I agree that if she's not communicating verbally yet try to teach her a few basic signs (e.g., "more", "help", "please," and common things she often wants).
It's certainly not lost on her that you have a new baby in the house, and that you're in a new place, and she may be having a hard time fitting that all together and finding her place. Kids are so perceptive! There are a lot of changes going on for her and you right now. She may just want to make sure she doesn't miss out on your attention. Really praise those moments when she's not screaming and try your best to ignore the tantrums (having a 3 1/2 yr old who still has her occasional tantrum, I certainly understand how hard it can be sometimes).
If screaming or crying because she's in pain, then it's likely that you would know it and that it would always be there. If that's the case then take her to the pediatrician, but it's more likely that it's mainly a behavioral thing (possibly compounded by teething, etc). Wish you the best! And be sure you make a little time for yourself and you and your spouse. Easier said than done, but your sanity is in your children's best interest.