Can't send MMS while connected to Wifi

[ctmason39]

I have a sprint gs5, and i am involved with multiple group messages with my friends. However, whenever i want to send a group text or any other MMS, i have to disconnect from wifi for the message to send. I can still recieve messages perfectly fine while wifi is on though. Also, my mom has the same phone as me and she doesnt have this issue. Can anyone give me a solution?