I typed a long message and it was converted to a multimedia message. When I press the send button it shows "sending" but never shows "sent". How do I know it has been sent or not?
It hasn't. The status would change if the message went through. Now you'll have to check you MMS settings from
-> Settings -> Multimedia message settings and your MMS APN from
Settings -> Wireless -> Mobile networks -> Access point names (or
Settings -> More.. -> Mobile networks -> Access point names in newer versions).
After you have corrected these and verified that your carrier/operator has enabled MMS on your account, the message should be sent. Or you have to long-press it and select