Just some random questions:
- is your data turned on when you are sending photos? Maybe try disabling Wi-Fi and only having your mobile data turned on while sending photos - I find sending is faster that way (maybe it's just me, but it's worth a shot!)
- what texting app are you using? Is that app set as your default texting app?
- are the intended recipients of the pictures telling you your photos are not being delivered? And their data is enabled, etc.?