Its possible to wire 1 sonoff to these type of 3 way switch wiring using GPIO 14 ?
The ones that i have seen online all have the light and the load cables on one switch but on my set up the load is on one switch and the light is on another.
It’s not possible the way you have your circuit currently configured.
You need to have mains voltage supplied to the sonoff all the time. Then you need to disconnect the mains power to your light switches. Then you need to connect your light switches in series either between ground and GPIO14 or 3.3v and GPIO14 on the sonoff (depending on how you have the firmware set up). you will likely need a pullup/pulldown resistor somewhere in your switch circuit as well.
I would recommend that you get someone knowledgeable in electrical circuits to help you. At a minimum you’ll probably have to pull a mains power cable to the sonoff.
If you have live and neutral at each switch location you could use a Sonoff T1 or USA at each point and have your bulb attached to one switch and do the rest in software. Although you will probably have to rejig the wiring a bit.