awww sucks about your birthday. Your mums partener sounds like a right dick head from the impression i got when reading.
Enjoy the real day dude. Dont bother with your parent(s), just go out with some mates and chill there... they pretty such screwed it up for you in the first place acting like children o_O. Apart from you losing your joint; which is dang annoying, especialy when it turns up in your hand all along.... I do that alot, lol.