Being sick and stressed can definitely raise your blood pressure even if your on the meds. Guessing you're taking your BP at home. Those machines aren't always accurate so in addition to calling your doc as marc suggested, tell him you want to come in for a 5 min visit so that he can check the accuracy of your machine. Basically, he'll take your BP as he normally would then you take it with the machine. If the numbers are different, then your machine isn't working right.
I had to do this about 6 months ago. Was taking my BP at home and it was scary high - 180/110 or 195/115 - scared the sh*t out of me - went on for about 2 months. Finally called the doc and he said come in with the machine - he took my BP and it was 110/80 then I took it with the machine and it was 150/99. I left the machine in his garbage can on my way out.