My phone storage is low, but how? Why?

[Erica]

So I'm using a samsung boost phone. I'm not sure the model but its similar to the first android.
when I fist got it, I had Tumblr, Facebook, Youtube, Instagram, and Words with friends. Then I got the Twitter app and even if I deleted all the other apps, I cant have more than Twitter and Facebook. Now its saying I can only have one at a time. I'm constantly closing the cashe and setting, and uninstalled a lot. I uninstalled the Google Playstore. My Gmail app that came with the phone...I even uninstalled and reinstalled Twitter.
Whats wrong? How do I fix this?