I would advise you to NOT go to the ER as it will be a big waste of time, money, and you won't get any answers. The ER is only there to treat emergencies and you are not having an emergency. One look at you and to hear your story of how this has been ongoing for a year and they will send you on your way and will refer you to a clinic for Outpatient care. THE ER and HOSPITALS do NOT provide outpt care to non-emergent visits! I think a more likely situation is you are young, 21... could be a little anemic from heavy periods and another likely theory very common amongst young girls is having a strong vasovagal response... like you can feel faint and then a little flushed, hot, tingly, out of it when the blood pools in the legs during such instances as getting up too fast from sitting down, or even having a bowel movement. It is really common. I actually had a strong vasovagal reaction when i was getting a tattoo and actually passed out on the floor when i was a teen. If you are sitting for long periods being still and tense and then you go to stand up, then yeah, you are gonna see floaters or feel faint. I think you should find an outpatient clinic that you can go to, or to a CVS 24 hours pharmacy clinic. Have them draw basic labwork such as CBC, CMP, and thyroid.