Suggest Treatment For Low BP And Lightheadedness While Taking Valsartan

I use to take daily 1/day diltiazem cd 180 mg & valsartan/hctz160/12.5. I am now taking only the valsartan since this past September because my pressure was low. I am now having more continuous days with pressure being low ( below 90 over below 70) and getting very light headed. I am wondering if I can take my meds every other day instead of daily? I skipped 2 days and then the third day it was 135+/88+ so I took my valsartan on the third day. Or should I take the diltiazem instead of valsartan?