Annoying burning in vagina from time to time.

For about 7 years now I have had an annoying burning feeling in my vegina from time to time. The occurences are random, I've never had sex or anything and I'm 18. This has been going on since I was around 13-14 and it just randomly started one day. From then on, at random intervals, usually after I go to the bathroom, I get this light burning sensation around where I pee/vagina area. It never itches, or smells or anything. I don't have an infection, I'm almost certain, so I can't imagine what could be causing this.

Sometimes it gets very annoying and the burning gets worse. I find that splashes of cold water helps a little, or perhaps I'm just thinking it does. The burning feeling can last up to ten minutes to three hours until I finally notice it's starting to go away.

Does anyone know what this is? Or am I just noticing this now and I have always had it? It's nothing dangerous, right? Since this has been happening to me, on and off for years.

Please help!