That would be a good Twilight Zone episode, as you open your eyes to find yourself in the final stages of unmedicated labor.
You know what, I’d take it. No woman could ever hold childbirth over my head in an argument ever again.
I wouldn’t say the OP is lying, some people are like that.
I’ve no idea the cause but his GF isn’t the only woman that suffers from lack of ambulatory co-ordination afterwards.
Maybe shes faking the deer like walking and not faking the orgasm.
A few weeks ago I was getting a pounding headache immediately after an orgasm. The first time I didn’t relate the orgasm to the headache. When it happened again and again, I knew that it was. I looked it up.
This is it: Sex headaches - Symptoms and causes - Mayo Clinic
It’s not pleasant, but I’m not about to give up sex or masturbating because of a bad headache. I don’t care how intense it is. I can take it, damn it!
I had that for a couple years in high school, then it went away for another handful of years, then it came back again…and now I’m in the off season for it.
Honestly some of the worst headaches I’ve ever gotten, I don’t look forward to when they rear their ugly head again.
My husband can’t walk after an orgasm either. I didn’t think that it was anything special because almost all the guys I ever had sex with couldn’t either.
What? Rolling over and falling asleep doesn’t count?
Mine were piercing headaches also. Strange ones, too. Sometimes just a few sharp pains and other times constant pounding for hours. I haven’t had one in about three weeks. Crossing my fingers that they stay away…
You could call it an I Scream headache.
Anecdote in support of the OP: I can’t walk after orgasm no matter who I’m with; wifey, girlfriend or mistress. Then again, I can’t walk before or after, well anything. 
So I guess anecdote fail.
In the country famous for love, this must happen frequently enough that there is a French phrase for it: La petite mort
And they named it the little death?
How romantic LOL
That doesn’t mean “can’t walk after orgasm”.
It’s just the French slang term for orgasm.
and always makes me think of this cover by Phil Foglio for Xxxenophile #9
Some girls are really shaky after an orgasm though. Seen it many times.
We get it, you vape.
Happened to me in the opposite direction-- one time after mutual masturbation in the shower, the orgasm my then-girlfriend gave me was so intense I had to get out of the shower and assume the recovery position on the floor for a couple minutes.
Now when she says,“Not tonight, I have a headache” I know what she’s been up to before I got into bed!"
Articles on vasovagal syncope or other types of syncope may be relevant and of interest. (If googling, get ready to sift through a ton of links to porn videos in order to find treatment advice.)
I’ve witnessed a complete loss of consciousness during an orgasm-induced episode and it was very frightening to watch.
That would freak me out. I like giving my gf huge orgasms but she needs to be able to handle her shit. No passing out, no screaming like a banshee, no collapsing into a heap. Those things aren’t turn-ons to me in any way.
If she’s already had her orgasm, why should she care what turns you on?