Im having problems playing this game, alot of times when i fight against some Enemy's and im about to kill them, there HP will go right back to full... I had one occasion when i was fighting inside that Hotel with the escaped convicts that there HP would stay Full and never go down..

Whats the issue ?

Are you using a Trainer?

Stimpaks, they use them when low on HP. Caught a ganger while in VATS sticking a stimpak in his gut, went from 3 lines to full health.