The full verse of Matt 5:17-19 reads:
Jesus said to his disciples: "Do not think that I have come to abolish the law or the prophets. I have come not to abolish but to fulfill. Amen, I say to you, until heaven and earth pass away, not the smallest letter or the smallest part of a letter will pass from the law, until all things have taken place. Therefore, whoever breaks one of the least of these commandments and teaches others to do so will be called least in the Kingdom of heaven. But whoever obeys and teach these commandments will be called greatest in the Kingdom of heaven.
Emphasis mine, on the most important part, which you left out.
As I said previously, the Mosaic Law in Leviticus concerning all sorts of things was meant only for the Hebrews until such time that the Messiah would come and fulfill the Law. Jews don't accept Christ as the Messiah, which is why they still follow the Law...no pork or shellfish, for example.
With the coming of Christ, his death, and resurrection, God forged a new covenant with mankind. As a former Catholic yourself, I'm sure I don't need to get into a detailed explanation of what that meant...but if needed, I will.
Your Catholic co-workers apparently need a refresher on RC doctrine if they're telling you gays go to hell. Again, being gay is not a sin. Sexual acts are the sin, for everyone, outside the bonds of marriage in the Catholic Church. You're correct that constantly sinning and confessing the same sin repeatedly doesn't mean you'll be forgiven that sin. It doesn't mean you're hell-bound, either. God judges all of us individually when our time on this Earth is done, on our faith and, as Catholicism teaches, on our good works.
You're wrong tho when, as your co-workers said unrepentant gays go to hell, you say it's "intolerant" of them. Even if they were correct, it has nothing to do with Catholic/Christian tolerance towards gays...sexual acts are far from the only sins. Again, being gay is not in any way sinful according to scripture, and Catholic doctrine. And just to add...nobody goes to hell for eating meat on Fridays (which is only during Lent, one of the changes brought about after Vatican II in 1967).
An important point...about blanket accusations: By condemning or blaming the entire group for the actions, words, and beliefs of some, is patently wrong. Doing so is blatant intellectual dishonesty. No, you don't have to jack-up your phone bill by calling every individual Christian for their own opinions or beliefs, but instead of saying "Christians are anti-gay" you can more accurately say "Some Christians are anti-gay".
I would hope I'm a nice person...but I've certainly been an arsewipe at times, like most people. As far as I've seen, you're probably a nice person as well, and I certainly give you kudos for the civil discussion...as I'm sure you're aware, far too many people simply cannot have a discussion/debate over such a hot topic like religion without things regressing to hateful name-calling and vile accusations pretty quickly.
I can't speak for all religious people, nor all Christians...I can only speak for myself as a Catholic, and tell you what Catholic doctrine says. No major changes in doctrinal issues in the Catholic Church have been changed or re-interpreted with the times. Changes brought about in Vatican II were non-scriptural...and included things like allowing mass to be said in any language, not solely Latin...and various other traditional stances. Catholicism very rarely makes any changes...and that's what brought about the Schism and the Reformation. Protestants change...the Catholic Church doesn't.
Sorry for the wall-o-text reply, I just want to be sure I've addressed as many points you made as I can. To sum it up, I do find comfort in my faith, The Church, and Christ. I won't get into the whole story, but when I was growing up, I...like most gays...knew I was "different" in that way, and I was absolutely petrified with fear over it. I hid it pretty well...but most nights, I cried and I prayed so hard, so often, for God to "fix" me.
Needless to say, God didn't fix my being gay...but through His mercy and love for me, and for all of us, He hasn't rejected me either. That's hard to explain, and I don't expect you to fully understand why my faith in God and His Church is very important to me. God hasn't turned His back on me, nor can I turn my back on Him.
Sorry again for rambling...hopefully I've at least explained what I could well enough, and if you have any questions I'm happy to address what I'm able to. Cheers!