I Have Been Diagnosed With Afib And Was Put On

I have been diagnosed with Afib and was put on xarelto to thin my blood. Also perscribed was carvedilol 6.25mg. and Losartan 25Mg. Since then I had one cancerous breast removed. Prior to surgery I was taken off all heart medications and am back on zarelto and carvedilol but Losartan makes my B.P. drop to 100 or even low 90's. even if I take just half a pill. Question: Do both carvelilol and losartan basically lower B.P. and are they equally necessary?