Occam's Razor dictates a very simple answer to his situation. He must be a pony who has lost their mind to a fantastical world of delirium and madness or had their mind tinkered with in some way. The idea that he's a trans-dimensional being that ended up in a foreign universe - in a native body and speaking the native language along with reading it - is laughably impossible. He'd be more insane believing this possibility than admitting to it's absurdity.

The problem now lies with trying to figure out what happened to him and trying to acclimate with the culture that's wildly different from what he "knows." It shouldn't be too bad as the pony society seems nice enough. Except, there's a few social nuances regarding the low stallion population and apparent gender inequality that rather bother him. Hopefully it'll get sorted out soon with the help of the ponies and a mind healer.

An Equestria has herds story told from everypony's perspective but the protagonists. Will talk about mature concepts and relationships, but whether it will contain sex or not is still under consideration. A world building exercise for exploring the concept of gender ratio issues coupled with herds in a sapient pony race along with how those herds always have a lead mare.