My number isnt sending back double texts anymore, instead its replying to me? worried somebody is on the other side

I've been texting my number reminders and random stuff for fun for a while. I've even sent personal information before like login info to remember. I know that it's normal for your own number to send you double texts but just recently mine stopped doing that, but I overlooked it thinking it was a part of a new update or something, which apparently it's not. The scariest part is that instead of sending double texts it replied to a question I sent myself with "Nah". Somebody please help lol nobody has been able to help me with this and I'm not sure what I should do.