Hi Joe,
Touching on Nick's point it does sound like you are creating a loop. Eric's point sounds like it's the best way forward. You will need to configure stacking if it hasn't been done already.
Once stacking is configured, you will need to configure link aggregation on the pfsense side first, by creating and building a "LAGG" with the interfaces you are trying to utilize. Once done create your link sharing LACP ports on the switch, 1:49-50, 2:49-50.