You are doing the right thing on valid and correct advice from the priest. A priest who acted differently is much similar to one who doesn’t see the difference between artificial birth control and natural family planning, so is indifferent to both. It’s not a “1962 thing”, it’s a doctrine of the Church, stated clearly in the Bible itself: “neither fornicators, nor thieves, nor adulterers, nor the greedy…shall inherit the Kingdom of Heaven.”
I’ll leave it to others here how such a reaction is proof-positive that your boyfriend isn’t in it for “you”, or the “long haul”, or marriage, but for instant carnal gratification and easy and frequent access to sex. He’s still a Catholic - in case some try to declare him a heretic - but just a sinful one, as we all are, but, sadly, unrepentantly sinful and seemingly unwilling to repent, as the Holy Spirit has not convicted him of sin in his soul, or he hath hardened his heart. The best, the only way to proceed is to move out, and let him react, and see what he does - if he wants a proper relationship - marriage, and not just sex - he’ll get over it.
I would normally say the right thing is to get married - but, having gone down the path that you have, and seeing how your boyfriend reacted, makes me doubt the wisdom of such a decision, to join in unbreakable matrimony with such a partner; although only you can decide, stubbornly unrepentant sin and vitriol and sarcasm against Catholic teachings and a faithful priest do not make the picture shine.
As far as living together without fornicating, it is possible, and, lest I think myself saintly, it doesn’t require a great deal of willpower (of which I am in short supply): I lived with, as circumstances demanded, a female roommate for nearly two years, probably half of which with no other roommate. As a Muslim, I co-habitated with a woman I was engaged to (and, actually, had carnal relations with for the once and only time that I shall, before we co-habitated), and, after converting to Christianity, remained living with her for almost a year - that year was the lion’s share of the no-other-roommates time - without engaging (nor, honestly, being greatly tempted to, thank the Lord for the graces he hath heaped upon me) in carnal relations a single time during the entire span. (And, at first, having to divert relatively heavy and constant advances.) Near occasion of sin, yes, but it doesn’t always lead to sin - it only usually does, so, for wisdom and safety, situations as such should be avoided if it is possible to avoid them.
“Trying” not to sleep in the same bed together is a cop-out. Maybe lust can overtake one due to concupiscence, in the “heat of the moment”, but where one will sleep within a property one has rights to is fully under the control of the will even in unregenerate man. “Sleeping in the same bed together” can’t overtake one like lust, unless it is a direct result of first being overtaken by lust and immediately falling asleep (this happens in American movies, but I don’t know if it happens in real life).
In your situation, since you have since relapsed, and on the direction of your confessor, that is not an appropriate solution, unless the alternative would be homelessness. It wasn’t an appropriate solution for me, either, but, being the sinner I am, it was the easiest, the “path of least resistance” or of inertia.
All it takes are the graces of Christ, the Church, and the Sacraments, absolution, and, accompanying that resolution, contrition and a firm and true resolution to not fall in to old behavior or to repeat the sin. As I was less adapted to sexual behavior, it was undoubtedly easier for me, but, with grace, all things are possible. “I can do everything through Christ who giveth me strength.”
Edit: reading former posts, the above is merely a more detailed exposition (especially of the “live like siblings” part) of a multiple choice question posed earlier:
- Live like siblings - failed.
- Marriage - not an option, and probably not wise seeing your boyfriend’s reaction.
- Move out.