Welcome to the forum.
First and foremost, I hope you can gain the correct perspective on genital warts: a somewhat unpleasant inconvenience, but no more than that. Certainly not an important health problem, with rare exceptions. Also, it take months and soemtimes years before warts appear after acquiring the HPV infection that causes them. To your specific questions:
1) Yes, you could have been the source of your partner's HPV infection. But you'll never know for certain. It is not possible (and for the most part not necessary) to know when and from whom most HPV infections were acquired.
2) You have been repeatedly exposed to your partner's HPV infection for a long time, and could have been the source. If you were not the source, you can assume you have been infected -- whether or not you devlop overt warts. There is nothing to be done at this point except to be on the lookout for warts and seek medical evaluation if warts appear.
3) Once someone is infected with a particular HPV strain, s/he probably is immune to a new infection with the same type. Couples probably do not "ping pong" their HPV infections back and forth.
4) The large majority of genital warts resolve entirely within several months, sometimes a year or two, and do not recur. It's possible, but unusual.
5) The "low risk" types of HPV, i.e. those that cause warts, rarely cause any important health problem, regardless of immune system problems. In any case, there is no reason to suppose either you or your partner have any immune system impairment, so this really shouldn't be a worry.
Please understand that almost all sexually active persons acquire HPV at one time or another; and that probably 10-20% of all persons have overt genital warts at some time. It really should not be nearly as big a deal as you seem to be making it. Genital HPV is a normal and expected consequence of human sexuality. Of course nobody wants genital warts, but as I said, it's an inconvenience, not an important health problem. I hope you and your fiance are avoiding the "blame game". Just deal with her warts and stop worrying about it.
I hope this helps give you some perspective on a very common and not particularly serious problem.
Regards-- HHH, MD
No, neither of you is likely to be "contagious forever". As I said, most HPV infections clear up, cause no further clinical problem, and cannot be transmitted. Viral DNA may (usually? always?) persist in tissues, with a potential for late recurrence and transmission. But these are uncommon, and one the virus can no longer be detected by standard tests, and overt warts or pap abnormalities are cleared up, usually there is no future problem of any kind.
Thank you for your help. We aren't blaming each other. I actually would prefer she had it first because I've been blaming myself. She is the same way. We are going to do our best to put it in the proper perspective. Hopefully it won't matter in the future as obviously we are getting married and spending the rest of our lives together, but if we were to split up in the future, would we be able to give someone else hpv? I guess I mean is it contagious forever?