Pain in my back

This is hard to explain, but for the past couple of hours I've been getting waves of pain in the right hand side of my back, round about waist level. They only last a few seconds, but are hapening every couple of minutes or so. I'm 22 weeks and 3 days and have had back aches for the past few weeks but never a pain like this. Went shopping today with hubby and while we were walking around i got a stictch in my right hand side and thats what this pain is like, but not constant, just coming in waves. Starting to freak me out a bit, cause no matter which way I sit or lie, it's hasn't stopped it. Bubby is still kicking away but is this something normal or should I be worried?
Thanks everyone in advance

I'm no expert but it maybe siatica! (Not sure if I spelled that correctly)
It is quite common in pregnancy and can be quite painful. I suffered from it and it probably started around 25weeks..It was on my right hand side just below my hip bone.

All the pressure on your nerves in your back from bubs and everything growing and stretching!

Maybe someone else might have a suggestion but I would just go and get it checked just to ease your mind!!