i dont know what to do anymore i ghosted this one guy and now he keeps bugging me

it was my last ex I never really did break up with him i just stopped answering his calls and texts and pretty much disappeared and now he's like is there a reason why you arent replying and wants me to call him. i dont want to call him or respond i just want to stay disappeared and silent but i have a feeling if i do respond it will cause a massive argument because the reason i stopped all contact was because he kept looking at other womens photos in front of me and i kept feeling like crap so i just left and cut all contact. i felt like a placeholder like i wasnt worth anything and was only there to satisfy a need until he found someone worth anything