Need motivation!!

Hello !Well I am 4'11 and 145. I have lost so much weight being from 185 but I cant seem to loose any more. I have only lost 4 pounds since sept ! I feel like I can never be under 140. I have never been that tiny since like 6th grade. Is it even possible to be 4 sizes smaller ? I feel like I have been stuck in this size/weight my entire life. It would be the best thing ever if I went to a size 6 that would be motivating