blood pressure Question

so i had been admitted to the hsp twice in one week due to gestational hypertension. bp ranging 138/84- 154/94 which ob said is not to bad (having a headache most of the time at 26 weeks is getting annoying). i been put on hy-po-tone 250mg to keep it down. ob adviced me to take my bp before taking the medication, to make sure i dont get low bp. so when my bp is above 125/70 i take one (1 tablet 8 hourly) then i start getting a worse headache, and then take my bp an hour later, and everytime it increases. i started monitoring this from monday. what can be causing this. i feel horrible every single day, and am not allowed to take any medication for headaches even though they are pregnancy save due to me taking bp medication. (on dont want my bp getting low and apparently headaches meds makes it lower)

this is from this morning until now. note that i haven't taken meds this morning when i woke up, because of bp being a bit low