Had a spinal tap last year, resulted in a spinal tap headache, it resolved. Have pressure/pain in back of head when sit/stand up again, is this related?

Unlikely to be pbm. The spinal headache you had originally is thought due to pressure change brought when the hole in your dura (cord cover) is leaking after the procedure is done.With time this closes over. Any new headache yo have a year later is likely related to other issues. Common triggers are stress, dehydration, lack of sleep, irregular feeding patterns and illness.