Hi,
How are you?
Generally headaches which occur or get worse on standing up and bending forwards are sinus headache.
Other cause of headache when standing up is head rush which occurs due to sudden rush of blood from feet to the head.
Do have runny nose or post nasal drip?
I think you need to get yourself clinically evaluated. In the meantime you can take OTC pain killers, sleep adequately and avoid caffeine and alcohol.
Take care!
It sounds like you should get this troubleshooted by your doc or a specialist asap.