what should i do?

i work at a grocery store that gives me really good hours and i absolutely need this job financially. but i'm 16 years old and a few months ago my 20 year old coworker and i hooked up, even though i sometimes expressed discomfort with what we were doing, he kept going so i kind of just went with it despite being kind of doubtful. nobody ever found out as far as i know, but he assaults girls we work with sometimes. he keeps asking me for nudes and to hook up lately, and even though i have a boyfriend he said he doesn't care. was i assaulted and am i being harassed now? the place i work with is really sexist and doesn't do anything about this kind of thing so what should i do? leaving isn't an option for me at this time