relationship issues

so my ex and i have never stopped talking since we broke up because we still like each other. last night we decided to give it another shot because we know each other better. but the issue is we both are afraid of cheating so he came up with the idea to be in an open relationship at the time i thought i’d be okay with t but i don’t think i am anymore. i want to give myself the chance to be loyal to someone but i don’t want to lose him. also when we event together he got jealous when i talked to other guys but i let him do his thing. what do i do?