Crazy huge dude

Ok, my ex girlfriend is going out with this crazy-ingly huge muscled dude and he wants to kick my ass and I am puny and scared. So I need to know where and how I can get a knife that is small and how I can carry it around my body at all times as to use it in case of defense (and defense only!).

I'm seriously scared and hope you guys can tell me how I can do this?

>>1
        Buy a pack of cigarettes and a bottle of rubbing alcholol.  put the cigarettes at the bottom of a bowel and pour the alcohol on top until they are completely covered.  wait for all the alcohol to evaporate and you have a black sludge at the bottom of the bowel.  The sludge is a highly concentrated mixture of all the nicotine and other toxins that were in those cigarettes.  Take a needle and coat it with the shit.  poke im with the needle.  This will cause a heartattack in about 15-20 seconds.  the toxins will disolve in the blood and be untraceble, and if he smokes it will be absolutely undetectable anyways.