iPhone security compromised?

I am concerned about my personal information on my iPhone. Today I apparently created a group text with 2 people, who I have no clue who they were but somehow had their numbers saved into my phone. The text to these people included messages that I had sent and received from my girlfriend today. The messages, which were separate while we spoke, were combined into one large paragraph and sent to these people who I do not know. I am concerned that I have been hacked and am very concerned about the security of everything on my iPhone now. Please help.