i usually have low blood pressure and at my last visit I said to my ob i had been feeling dizzy etc, my BP was 105/65 compared to 120/75 from the previous month. Low pressure is better than high... just remember not to push yourself too hard and when you sit down, try to put your feet up. My ob said when you are pregnant everything relaxes, including your veins so they open wider than normal meaning the blood rushes to your feet when sitting, so stand slowly or you will feel very dizzy as it takes longer than normal for the blood to get back to your head!
Good luck for the rest of the pregnancy and just keep a record of it if you are concerned