Immaculate conception? ;)
Mate, geldings don't even fire blanks, they just don't fire at all. Unless he's a rig, and even then there is an extremely low chance that he would be capeable of getting a mare pregant, then it's impossible that your mare is in foal.
The whole point of gelding a colt is so that he can't breed.
If she's acting out of sorts, I would get your vet to give her a once over. Possibly she's got a belly full of gas that's getting her bloated and making her irritable.