Light headed spells

When I was pregnant I would get random light headed spells my OB always told me they would go away after I gave birth and to lay on my side. I am 6 months PP and have been experiencing this again and it comes on randomly I can be sitting down, laying down or standing up my last blood work results came back normal except for low Vitamin D and I have not had my period in over a week but all my tests are coming back negative. My next appointment isn't until June and they have no openings or cancelled appointments.

Has this happened to anyone else?