I have been bedridden doing nothing for who knows how long everytime i stand up i feel like i'm gonna pass out how do i fix this?

It is not feasible to provide a meaningful opinion without taking additional history, physical examination and may be some tests. It would be prudent to see your doctor and discuss if you may be depressed. Counter-intuitive as it may seem, exercise may help. Start with low intensity exercise such as walking and gradually increase the intensity as tolerated. Drink more water. Wish you good health!

Perhaps you suffer orthostatic hypotension where your blood pressure drops when standing. This could be due to dehydration, and prolonged bedrest may be a profound contributor. It would be wise to have an evaluation by a physician who could check postural blood pressure and pulse, and also screen cardiac, hematological, and metabolic functions.

You’re experiencing Orthostasis, which is common when bedridden or deconditioned. This can also be caused by other medical conditions. Normally, when you go from flat to an upright position, your body works to send adequate blood flow against gravity. Confirm with Orthastatic BP study. Do leg exercises in bed routinely and before getting up. Change position slowly so your body has time to adjust.