Stretching or something different??

Hey,
I have a worry about something, but it's somewhat difficult to explain. I am 18 and I am sexually active and I haven't really had any problems at all, but I've noticed that it seems like my vaginal opening (this is very difficult for me to describe so bare with me), not skin, but something like my inner labia surrounding it. I'm positive it's not my inner labia, and I don't really look at my vagina often so I am really worried if this is normal or not. It doesn't hurt when I touch it or have sex, there is no funny smell, I feel normal. Is my vaginal opening just stretching? I am worried that my inner vagina may be coming out. It somewhat resembles inner labia just surrounding the opening of my vagina and smaller. I hope you can understand my description and help me know what's happening. I feel perfectly fine but I'm just worried that this may be something more serious. Thank you and please get back to me as soon as you can.