adding custom words via typing them in abc mode not working

i was tryna add "prolly" to the dictionary as i use it when texting all the time. yet even after typing it out manually, pressing * and then pressing the second option in the menu to add the word, after accepting each letter manually with the centre button of my phone, when I try to type it in "english" mode it simply doesnt appear. same goes for "doesnt" actually. (i usually omit contractions when typing casually theyre not really needed and it makes typing easier.)