Well, the best idea would be to take another pregnancy test. If you are missing your period for a month already it is best to take the test. Also you can go and see you ginecologist, who can also make the test. If you are pregnant and are willing to take of the baby you will sooner or later have to tell your mom. Maybe she will be angry at the begining but out of my experience as I talked to young mother, their moms were not long angry at them but have been very suportive. The best way would be to tell your mother as soon as you know if you are pregnant or not. So you two will both have time to adapt to the new situation. Don't wait until your pregnany will start to show. Then she will be even more angry because you tried to hide it from her and will even be dissapointed that you didn't come to her with your problems.
I hope everything will turn out all right. And if you are not pregnant be more carefull next time you have sex.
Jauzi