My two cents:
If your boyfriend can’t accept that before you even met him, you sinned (in a way that sounds unlikely to affect him as you did not actually have sex or go “super far” so you probably did not contract an STD), but repented and resolved to not do it again, then he isn’t a good partner for you.
Unfortunately, some people are not as able as God to forgive past sexual conduct. They get all hung up thinking about their partner with another person or worrying that their partner might do this type of thing again. This type of person really needs an exclusive partner who has never done anything sexual with anyone but them. There are plenty of other people out there who will say the past is past and not mind as long as you act morally now going forward.
You also did not do this while you were with your current boyfriend, so you could not have had any intent to hurt him or any hurtful disregard of his feelings when you had not even met him.
I would tell the boyfriend that you’re sorry he feels upset, but as this happened before you two met and you have already repented and been forgiven by God and are not repeating the behavior, you think it would be better to break up as you cannot be with a man who is unable to “meet you where you are” and accept you. Good luck.