Heal magic don't cure you they damage you so don't let a healer (cleric or similar) cast any heal spell on you.
If a cleric or similar class use his turn undead you will receive damage
Yo don't have Constitution so you need the charisma mod to gain the extra hit point
If you hit point reach 0 you are not disable you are dead
All of the undead templates, heck even the undead type look ludicrously good. So, any ideas on how to mechanically represent such a change without straying too far into the cheese?
in the end, most of it is a question to ask the GM, but the general undead creature type rules should apply:
• No Constitution score. Undead use their Charisma scores in place of their Constitution scores when calculating hit points, Fortitude saves, and any special ability that relies on Constitution (such as when calculating a breath weapon’s DC).
• Immunity to all mind-affecting effects (charms, compulsions, morale effects, patterns, and phantasms).
• Immunity to bleed, death effects, disease, paralysis, poison, sleep effects, and stunning.
• Not subject to nonlethal damage, ability drain, or energy drain. Immunity to damage to its physical ability scores (Constitution, Dexterity, and Strength), as well as to exhaustion and fatigue effects.
• Cannot heal damage on its own (over time) if it has no Intelligence score, although it can be healed by others (such as with inflict spells). Negative energy (such as an inflict spell) can heal undead creatures. The fast healing special quality works regardless of the creature’s Intelligence score. *
• Immunity to any effect that requires a Fortitude save (unless the effect also works on objects or is harmless).
• Not at risk of death from massive damage, but is immediately destroyed when reduced to 0 hit points.
• Not affected by raise dead and reincarnate spells or abilities.
Resurrection and true resurrection can affect undead creatures. These spells turn undead creatures back into the living creatures they were before becoming undead.
• Undead do not breathe, eat, or sleep.
*) Positive energy based spells like Cure Light Wounds harm undead instead of healing them, as per the spells' descriptions. A Cleric's positive channel energy would likewise would affect you as described (although if used to heal living targets, it doesn't hurt undead).
If a cleric or similar class use his turn undead you will receive damage
Clerics don't have Turn Undead in Pathfinder...
Instead of a full undead you could come back as something half way. Change your race to Dhampir instead of what your current race is. The Moroi born alternative would be a good fit. This gives you a lot of undead like traits but nothing really over powering or incredibly limiting.
You mentioned your character is a monk. If you did like most monks do and used CHA as a dump stat being undead may not be as good as it would seem. Your HP are probably going to be much lower as now you have a penalty instead of a bonus due to using your CHA bonus instead of your CON. This is also going to affect your fortitudes saves that you are not immune to.
"So the DM just made me undead, how can this work mechanically?"
Your GM is a necromancer in real life.
Reanimated Medium might be a better solution than just changing you to undead. It might be a better fit to just replace one of your monk levels with one of the Medium levels, rather than get screwy with the mechanics.