Does anyone know how blood pressure can change so dramatically in 5 minutes?

My BP has been up and down the whole pregnancy and have been diagnosed with Pregnancy Induced Hypertension and have been on medication for it (stopped taking them now - as my BP dropped to 110/60)

My BP was 160/90
5 mins later
My BP was 170/98
5 mins later
My BP was 148/77
5 Mins later
My BP was 156/85

I was put into hospital overnight for monitoring as bubs heartbeat was going up to 180+ while I was having "tightenings" and my vision was very blurry and I was extremely dizzy and disorientated.

I was discharged 24hrs later with BP of 136/70 and tightenings had lessen and bubs heart rate was back between 130-160

Just wondering if anyone has gone through the same thing or knows anything a bit more about blood pressure... I will be asking my GP on monday at my appt.. just thought id see if anyone on here could help in the meantime

Thanks!!