Jaspion

Hi everyone, this is the first time I post here. I play piano pretty well and I want to compose song melodies but I'm a bit confused about how to do that 'cos whenever I attempted to compose a full melody I realized afterwards that it was just an imitation of something I'd heard before. So I'm definitely not going for the "play what naturally comes to mind" thing lol I think I'm able to create original chord progressions & chord changes but I don't know how to create a truly original structure (verses & chorus length, number of syllabs...) My favorite kind of music is pop music made with synthesizers & drum machines (mainly late 80's stuff) and when I'm listenning to one of my fav songs I try to analyze how the melody was made but I don't go too far and end up wondering "how the hell did they do that?" and it still seems magical and unexplainable to me lol What advice would you give me so I could create melodies that really come from me? Does it require specific music knowledge? Is it possible to "imagine" melodies before sitting at the piano or is it better to seek for them by pressing keys? Note: english isn't my first language so excuse me if some sentences sound weird ;-) Thanks in advance.