I got talked into joining the army, but now i feel that i may not qualify medically?

I have a problem that i feel i may not have a way to fix. I enlisted into the army a few weeks ago and now regret doing so. I went to MEPS once, signed where everyone wanted me to, and swore in once. I then got with my recruiter and set up a new bank acct. with the armed forces bank. Previously to me going to MEPS I came to a recruiting office as a favor to a friend who was in the army and he had just got out of basic and came home for two weeks and he asked me to go up to the recruiting office and pretend to be interested because he was supposed to recruit somebody during his two weeks at home and if i at least pretended to be interested he thought it would get the other recruiters off of his back for not recruiting anyone. I really wasn't all that interested, but as we all know the recruiters get paid to make it sound like its too good of an opportunity to p up. But, in 2004, I was involved in a bad car wreck and had suffered a traumatic brain injury and was in a coma for 28 days, I'm really lucky to be alive and able to function as a normal person does and i told the recruiter this once he had "attached" himself to me and i got tons of phone calls everyday asking me when i was gonna join and he even came to my house once, and he said that i would be fine and had absolutely nothing to worry about. Finally, i ended up at MEPS and i did as my recruiter told which was to lie to them at MEPS and say that i was medically ok and never had been to a hospital as a patient and i signed. Why? Because im easily convinced and i believed that everything would be okay as far as medical worries because my recruiter insisted that I would be fine. Now, I have been getting weird headaches in the past 8 or 9 days where i can hardly even stand up without falling over atleast once a day, and im really worried that i have no way out of this without facing fines and/or jailtime. So, my question is... what options do i have to get myself out of this terrible situation?