I would say if the tests say negative most likely you are not pregnant.
I was just freaking out too because AF was over 2 weeks late for me which isn't normal for me. Another person in my
PR pointed out you can only really consider yourself "late" if you actually know when you ovulated and your period didn't show up 14 days later. A lot of things can make your period late, weight loss/gain, stress, hormone imbalance. If your tests aren't coming back positive try not to stress too much.
Now... if you are pregnant I doubt that your previous drug and alcohol use would effect the embryo much if at all. I would tell your doctor about it if you find you are pregnant but I don't believe you would have harmed the baby at this point, especially since if you did those things around the Christmas period and your last cycle started the dec 26th... even if you were pregnant now you wouldn't have been then.And because now you know that it is a possibility you should avoid those things until you have a definate answer.
Let us know how your testing goes. Good luck!