Is my blood pressure a little low? Or normal?

I have a home blood pressure monitor, Omron. In March/April it was very high due to excessive drinking. As high as 160/90. Im only 19 years old by the way, just turned 19 in March. But anyway, since ive became pregnant (NOT A RANDOM DRUNKEN PREGNANCY BY THE WAY!; im in a long term relationship with a wonderful man) and stopped drinking my blood pressure has been usually in the range of 123/89 to 110/60. Anyway, just took it and it was 110/51, i know the bottom number is lower than recommended, is this bad? And also, can pregnancy cause your blood pressure to lower? Ive always thought it could and thats one of the reasons i had a feeling i was pregnant. Answers would be awesome! Thanks! :)