I have a pain in my lower right stomach?

I've had it since early December. It's a very dull pain about an inch to the right and a little below my belly on. It lasts for a few minutes and then it goes away. It's normally the dull pain or just feels a little funny, but sometimes it hurts more like a spiking pain, but again it only lasts for a few minutes. I've been trying to take note of when it happens, and it's pretty much random. Laying down doesn't help or worsen it and it isn't particularly after I eat or walk or anything. I have been noticing that I felt a little gaseous usually when it comes lately. I've been getting my periods regularly each month. It's also just about right where my pant line is, so I thought maybe it could be caused by the pressure from that (I usually wear jeans). Sometimes it kind of feels itchy, but underneath my skin. I know it isn't appendicitis because it has been too long and it doesn't hurt enough for that. I have had this before about a year ago, but it didn't last this long and eventually went away altogether. Now it's back, and it's been around so long that I'm now getting concerned and am wondering what it could be. It feels as though if I were to do some vigorous stretching or exercise it would hurt a lot, like it would stretch or rip a muscle or whatever it is. I tried to lift my mattress today and it did make the pain worse. That's about all the information I can give.