You could always consider pull a Comic Book Industry Gambit and use a Retcon: your character was always female, and all interactions in the past with her are retroactively changed to reflect that or are handwaved as never happening if they weren't appropiate (like, for example, if your male character flirted with a female who is strictly uninterested in other females). This is the simplest solution if you can get everyone you have interacted with in the same page.
I will assume that you want to have some kind of character arc for this change, though. I would copy-paste and tweak a similar plot from the Baldur's Gate 2 game, where a excessively arrogan magician called Edwin searches and finally gets hold of a strange magical scroll fabled to be "too dangerous". He casts it, and all it does is change him into a woman. Hilarity might or might not ensue. The plot is eventually resolved by Edwin dispelling the effects of the scroll.
In your case, the plot will never be resolved with that. Also, your character, according to your wiki, is a marauder and not a magician. With that in mind, I propose the following:
Instead of the scroll Baldur's Gate used, make it an actual artifacl. A rod, a wand, anything. Then specify that its power is shapeshifting.
Have your character (and maybe other to tag along) be contacted by someone (a scholar?) to search ruins or whatever locations you can think of where the artifact might be.
Then you can do a couple of things depending on how fast you want this particular portion of the plot to go. You can just have your character recklessly touch or use the object (for whatever reason; it could be accidental) and releasing the spell on him. Or you could have the scholar/employer try the object on him once acquired. Why? Fear of it being broken, or fear that it would transform him into a rabbit forever. The accident is problably the best bet, since the second option really throws your employer into villain territory.
A third option I can think of that is relativelly painless and quick is to blame the change on a potion. Your character acquired it from some shady individual and, for some reason, decided to drink it. Maybe it was suppoused to be a really, really good healing potion, or a very expensive wine. Except it was nothing of that, and it was really a bottle filled with the Fantasia draught. Then you can have the shady individual drop to a side and never be seen, or start a plot about hunting him down for explanations and then elaborate a larger plot from there.
I will assume that you want to have some kind of character arc for this change, though. I would copy-paste and tweak a similar plot from the Baldur's Gate 2 game, where a excessively arrogan magician called Edwin searches and finally gets hold of a strange magical scroll fabled to be "too dangerous". He casts it, and all it does is change him into a woman. Hilarity might or might not ensue. The plot is eventually resolved by Edwin dispelling the effects of the scroll.
In your case, the plot will never be resolved with that. Also, your character, according to your wiki, is a marauder and not a magician. With that in mind, I propose the following:
Instead of the scroll Baldur's Gate used, make it an actual artifacl. A rod, a wand, anything. Then specify that its power is shapeshifting.
Have your character (and maybe other to tag along) be contacted by someone (a scholar?) to search ruins or whatever locations you can think of where the artifact might be.
Then you can do a couple of things depending on how fast you want this particular portion of the plot to go. You can just have your character recklessly touch or use the object (for whatever reason; it could be accidental) and releasing the spell on him. Or you could have the scholar/employer try the object on him once acquired. Why? Fear of it being broken, or fear that it would transform him into a rabbit forever. The accident is problably the best bet, since the second option really throws your employer into villain territory.
A third option I can think of that is relativelly painless and quick is to blame the change on a potion. Your character acquired it from some shady individual and, for some reason, decided to drink it. Maybe it was suppoused to be a really, really good healing potion, or a very expensive wine. Except it was nothing of that, and it was really a bottle filled with the Fantasia draught. Then you can have the shady individual drop to a side and never be seen, or start a plot about hunting him down for explanations and then elaborate a larger plot from there.