Yes, it's normal 
Mine's pretty low when not pregnant and at my last couple of appointments has been 96/55 (17weeks) and 90/69 (21 weeks) compared to 100/80 at booking (12 weeks).
From previous experience, it'll pretty much stay this low for the duration and my pulse will be fast (100-105, often) - even post delivery. They took blood from me last time worried I'd had a pph given my low bp/fast pulse combo the day after delivering... but, nope, not anemic.
Fifth pregnancy, and never fainted.
Definitely better to have low rather than high bp but if you have low bp and are symptomatic with it (light headed/fainting) then making sure you're properly hydrated can bring it up some, as will small regular meals/snacking. I am terrible with 'drinking enough'. Of course, the low bp may not be what is giving you your symptoms - anemia is another consideration.
Also, as for putting your life on hold for fear of fainting, remember, you will normally get physical clues that you're close to fainting - so long as you can read the cues and take evasive manouvres you can probably stall the faint long enough to be 'safe' or even avoid it altogether.
Have you spoken to you mw for advice/reassurance?