I Am 6 Weeks Post Op On A Mitral Valve

I am 6 weeks post op on a mitral valve prostheses, maze procedure for afib, arterial ligation, and bypass. I am 43 yrs old and have been recuperating ahead of schedule. I was in the yard slightly bent over not digging but skimming the dirt off the top when I started feeling light headed. I walked inside feeling really dizzy almost fainted. I checked my BP and it was 88/60 HR of 88bmp seemed low so I checked it again. It was 143/90 88bmp HR afterwards about 15 minutes I felt fine. Back to normal BP 109/70 87 BPM HR. Witch is about normal I take aspirin warfarin metoprolol 50mg and atorvastatin